diff --git a/src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/BlockedKeywordValidator.java b/src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/BlockedKeywordValidator.java
index 8b8b244..ef66c33 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/BlockedKeywordValidator.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/uploadvalidator/BlockedKeywordValidator.java
@@ -24,13 +24,13 @@
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Iterables;
-import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.entities.Patch;
 import com.google.gerrit.entities.Project;
 import com.google.gerrit.entities.Project.NameKey;
 import com.google.gerrit.extensions.annotations.Exports;
 import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.api.projects.ProjectConfigEntryType;
+import com.google.gerrit.extensions.client.DiffPreferencesInfo;
 import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.extensions.validators.CommentForValidation;
 import com.google.gerrit.extensions.validators.CommentValidationContext;
@@ -44,6 +44,10 @@
 import com.google.gerrit.server.git.validators.CommitValidationException;
 import com.google.gerrit.server.git.validators.CommitValidationListener;
 import com.google.gerrit.server.git.validators.CommitValidationMessage;
+import com.google.gerrit.server.patch.PatchList;
+import com.google.gerrit.server.patch.PatchListCache;
+import com.google.gerrit.server.patch.PatchListKey;
+import com.google.gerrit.server.patch.PatchListNotAvailableException;
 import com.google.gerrit.server.project.NoSuchProjectException;
 import com.google.inject.AbstractModule;
 import com.google.inject.Inject;
@@ -66,6 +70,7 @@
 import java.util.concurrent.ExecutionException;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import org.eclipse.jgit.diff.Edit;
 import org.eclipse.jgit.diff.RawText;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectLoader;
@@ -80,8 +85,6 @@
  * validator classes to run its list of blocked keywords against commit content and comments.
  */
 public class BlockedKeywordValidator implements CommitValidationListener, CommentValidator {
-  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
-
   // These keys are used for turning on specific validation elements.
   // i.e. enableSkipValidation = blockedKeyword will enabled skipRef and skipGroup checks
   // i.e. disabledValidation = blockedKeywordComments will disable the comment blocked keyword check
@@ -116,6 +119,7 @@
   private final GitRepositoryManager repoManager;
   private final LoadingCache<String, Pattern> patternCache;
   private final ContentTypeUtil contentTypeUtil;
+  private final PatchListCache patchListCache;
   private final ValidatorConfig validatorConfig;
 
   @Inject
@@ -125,12 +129,14 @@
       @Named(CACHE_NAME) LoadingCache<String, Pattern> patternCache,
       PluginConfigFactory cfgFactory,
       GitRepositoryManager repoManager,
+      PatchListCache patchListCache,
       ValidatorConfig validatorConfig) {
     this.pluginName = pluginName;
     this.patternCache = patternCache;
     this.cfgFactory = cfgFactory;
     this.repoManager = repoManager;
     this.contentTypeUtil = contentTypeUtil;
+    this.patchListCache = patchListCache;
     this.validatorConfig = validatorConfig;
   }
 
@@ -158,6 +164,7 @@
         try (Repository repo = repoManager.openRepository(receiveEvent.project.getNameKey())) {
           List<CommitValidationMessage> messages =
               performValidation(
+                  receiveEvent.project.getNameKey(),
                   repo,
                   receiveEvent.commit,
                   receiveEvent.revWalk,
@@ -169,7 +176,10 @@
           }
         }
       }
-    } catch (NoSuchProjectException | IOException | ExecutionException e) {
+    } catch (NoSuchProjectException
+        | IOException
+        | ExecutionException
+        | PatchListNotAvailableException e) {
       throw new CommitValidationException("failed to check on blocked keywords", e);
     }
     return Collections.emptyList();
@@ -205,15 +215,19 @@
 
   @VisibleForTesting
   List<CommitValidationMessage> performValidation(
+      Project.NameKey project,
       Repository repo,
       RevCommit c,
       RevWalk revWalk,
       ImmutableCollection<Pattern> blockedKeywordPatterns,
       PluginConfig cfg)
-      throws IOException, ExecutionException {
+      throws IOException, ExecutionException, PatchListNotAvailableException {
     List<CommitValidationMessage> messages = new LinkedList<>();
     checkCommitMessageForBlockedKeywords(blockedKeywordPatterns, messages, c.getFullMessage());
     Map<String, ObjectId> content = CommitUtils.getChangedContent(repo, c, revWalk);
+    PatchList patchList =
+        patchListCache.get(
+            PatchListKey.againstDefaultBase(c, DiffPreferencesInfo.Whitespace.IGNORE_NONE), project);
     for (String path : content.keySet()) {
       ObjectLoader ol = revWalk.getObjectReader().open(content.get(path));
       try (InputStream in = ol.openStream()) {
@@ -221,7 +235,8 @@
           continue;
         }
       }
-      checkFileForBlockedKeywords(blockedKeywordPatterns, messages, path, ol);
+      checkLineDiffForBlockedKeywords(
+          patchList.get(path).getEdits(), blockedKeywordPatterns, messages, path, ol);
     }
     return messages;
   }
@@ -252,18 +267,23 @@
     }
   }
 
-  private static void checkFileForBlockedKeywords(
+  private static void checkLineDiffForBlockedKeywords(
+      List<Edit> edits,
       ImmutableCollection<Pattern> blockedKeywordPatterns,
       List<CommitValidationMessage> messages,
       String path,
       ObjectLoader ol)
       throws IOException {
+    List<String> lines = new ArrayList<>();
     try (BufferedReader br =
         new BufferedReader(new InputStreamReader(ol.openStream(), StandardCharsets.UTF_8))) {
-      int line = 0;
       for (String l = br.readLine(); l != null; l = br.readLine()) {
-        line++;
-        checkLineForBlockedKeywords(blockedKeywordPatterns, messages, path, line, l);
+        lines.add(l);
+      }
+    }
+    for (Edit edit : edits) {
+      for (int i = edit.getBeginB(); i < edit.getEndB(); i++) {
+        checkLineForBlockedKeywords(blockedKeywordPatterns, messages, path, i + 1, lines.get(i));
       }
     }
   }
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 7c1cc23..aa7b0cf 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -143,7 +143,7 @@
 :    Patterns for blocked keywords.
 
     This check looks for blocked keywords in files. If the check finds an
-    blocked keyword the push will be rejected.
+    blocked keyword in the diff between the pushed commit and it's parent.
 
     To find a keyword it is possible to pass a regular expressions by
     blockedKeywordPattern.
diff --git a/src/test/java/com/googlesource/gerrit/plugins/uploadvalidator/BlockedKeywordValidatorTest.java b/src/test/java/com/googlesource/gerrit/plugins/uploadvalidator/BlockedKeywordValidatorTest.java
index c709622..245f2dc 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/uploadvalidator/BlockedKeywordValidatorTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/uploadvalidator/BlockedKeywordValidatorTest.java
@@ -17,11 +17,19 @@
 import static com.google.common.truth.Truth.assertThat;
 import static com.googlesource.gerrit.plugins.uploadvalidator.TestUtils.EMPTY_PLUGIN_CONFIG;
 import static com.googlesource.gerrit.plugins.uploadvalidator.TestUtils.PATTERN_CACHE;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.entities.Patch;
+import com.google.gerrit.entities.Project;
 import com.google.gerrit.server.git.validators.CommitValidationMessage;
+import com.google.gerrit.server.patch.PatchList;
+import com.google.gerrit.server.patch.PatchListCache;
+import com.google.gerrit.server.patch.PatchListEntry;
 import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
@@ -31,11 +39,26 @@
 import java.util.Set;
 import java.util.regex.Pattern;
 import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.diff.Edit;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.junit.Test;
 
 public class BlockedKeywordValidatorTest extends ValidatorTestCase {
+  /** Maps file names to content. */
+  private static final Map<String, String> FILE_CONTENTS =
+      ImmutableMap.of(
+          "bar.txt",
+          "$Id$\n"
+              + "$Header$\n"
+              + "$Author$\n"
+              + "processXFile($File::Find::name, $Config{$type});\n"
+              + "$Id: foo bar$\n",
+          "foo.txt",
+          "http://foo.bar.tld/?pw=myp4ssw0rdTefoobarstline2\n",
+          "foobar.txt",
+          "Testline1\n" + "Testline2\n" + "Testline3\n" + "Testline4");
+
   private static ImmutableMap<String, Pattern> getPatterns() {
     return ImmutableMap.<String, Pattern>builder()
         .put("myp4ssw0rd", Pattern.compile("myp4ssw0rd"))
@@ -46,39 +69,42 @@
 
   private RevCommit makeCommit(RevWalk rw) throws IOException, GitAPIException {
     Map<File, byte[]> files = new HashMap<>();
-    // invalid files
-    String content = "http://foo.bar.tld/?pw=myp4ssw0rdTefoobarstline2\n";
-    files.put(
-        new File(repo.getDirectory().getParent(), "foo.txt"),
-        content.getBytes(StandardCharsets.UTF_8));
-
-    content =
-        "$Id$\n"
-            + "$Header$\n"
-            + "$Author$\n"
-            + "processXFile($File::Find::name, $Config{$type});\n"
-            + "$Id: foo bar$\n";
-    files.put(
-        new File(repo.getDirectory().getParent(), "bar.txt"),
-        content.getBytes(StandardCharsets.UTF_8));
-
-    // valid file
-    content = "Testline1\n" + "Testline2\n" + "Testline3\n" + "Testline4";
-    files.put(
-        new File(repo.getDirectory().getParent(), "foobar.txt"),
-        content.getBytes(StandardCharsets.UTF_8));
+    for (Map.Entry<String, String> fileContents : FILE_CONTENTS.entrySet()) {
+      files.put(
+          new File(repo.getDirectory().getParent(), fileContents.getKey()),
+          fileContents.getValue().getBytes(StandardCharsets.UTF_8));
+    }
     return TestUtils.makeCommit(rw, repo, "Commit foobar with test files.", files);
   }
 
   @Test
-  public void testKeywords() throws Exception {
+  public void keywords() throws Exception {
+    // Mock the PatchListCache to return a diff for each file in our new commit
+    PatchListCache patchListCacheMock = mock(PatchListCache.class);
+    PatchList mockPatchList = mock(PatchList.class);
+    when(patchListCacheMock.get(any(), any(Project.NameKey.class))).thenReturn(mockPatchList);
+    for (Map.Entry<String, String> fileContent : FILE_CONTENTS.entrySet()) {
+      PatchListEntry file = mock(PatchListEntry.class);
+      when(file.getEdits())
+          .thenReturn(
+              ImmutableList.of(new Edit(0, 0, 0, numberOfLinesInString(fileContent.getValue()))));
+      when(mockPatchList.get(fileContent.getKey())).thenReturn(file);
+    }
+
     try (RevWalk rw = new RevWalk(repo)) {
       RevCommit c = makeCommit(rw);
       BlockedKeywordValidator validator =
           new BlockedKeywordValidator(
-              null, new ContentTypeUtil(PATTERN_CACHE), PATTERN_CACHE, null, null, null);
+              null,
+              new ContentTypeUtil(PATTERN_CACHE),
+              PATTERN_CACHE,
+              null,
+              null,
+              patchListCacheMock,
+              null);
       List<CommitValidationMessage> m =
-          validator.performValidation(repo, c, rw, getPatterns().values(), EMPTY_PLUGIN_CONFIG);
+          validator.performValidation(
+              Project.nameKey("project"), repo, c, rw, getPatterns().values(), EMPTY_PLUGIN_CONFIG);
       Set<String> expected =
           ImmutableSet.of(
               "ERROR: blocked keyword(s) found in: foo.txt (Line: 1)"
@@ -95,4 +121,8 @@
   public void validatorInactiveWhenConfigEmpty() {
     assertThat(BlockedKeywordValidator.isActive(EMPTY_PLUGIN_CONFIG)).isFalse();
   }
+
+  public static int numberOfLinesInString(String str) {
+    return str.length() - str.replace("\n", "").length();
+  }
 }
diff --git a/src/test/java/com/googlesource/gerrit/plugins/uploadvalidator/UploadValidatorIT.java b/src/test/java/com/googlesource/gerrit/plugins/uploadvalidator/UploadValidatorIT.java
index cafc18c..bee5418 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/uploadvalidator/UploadValidatorIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/uploadvalidator/UploadValidatorIT.java
@@ -244,4 +244,127 @@
     push.setPushOptions(ImmutableList.of("uploadvalidator~skip"));
     push.to("refs/heads/master").assertOkStatus();
   }
+
+  @Test
+  public void keywordExistsInFileButNotInDiff() throws Exception {
+    pushFactory
+        .create(
+            admin.newIdent(),
+            clone,
+            "Subject",
+            "file.txt",
+            "" + "blah \n" + "secr3t\n" + "blah" + "")
+        .to("refs/heads/master")
+        .assertOkStatus();
+    pushConfig(
+        Joiner.on("\n").join("[plugin \"uploadvalidator\"]", "    blockedKeywordPattern = secr3t"));
+    pushFactory
+        .create(
+            admin.newIdent(),
+            clone,
+            "Subject",
+            "file.txt",
+            "" + "blah \n" + "secr3t\n" + "foo" + "")
+        .to("refs/heads/master")
+        .assertOkStatus();
+  }
+
+  @Test
+  public void keywordExistsInNewFile() throws Exception {
+    pushConfig(
+        Joiner.on("\n").join("[plugin \"uploadvalidator\"]", "    blockedKeywordPattern = secr3t"));
+    pushFactory
+        .create(
+            admin.newIdent(),
+            clone,
+            "Subject",
+            "file.txt",
+            "" + "blah \n" + "secr3t\n" + "foo\n" + "secr3t")
+        .to("refs/heads/master")
+        .assertErrorStatus("blocked keywords");
+  }
+
+  @Test
+  public void keywordExistsInFileAndInDiff() throws Exception {
+    pushFactory
+        .create(
+            admin.newIdent(),
+            clone,
+            "Subject",
+            "file.txt",
+            "" + "blah \n" + "secr3t\n" + "blah" + "")
+        .to("refs/heads/master")
+        .assertOkStatus();
+    pushConfig(
+        Joiner.on("\n").join("[plugin \"uploadvalidator\"]", "    blockedKeywordPattern = secr3t"));
+    pushFactory
+        .create(
+            admin.newIdent(),
+            clone,
+            "Subject",
+            "file.txt",
+            "" + "blah \n" + "secr3t\n" + "blah\n" + "secr3t")
+        .to("refs/heads/master")
+        .assertErrorStatus("blocked keywords");
+  }
+
+  @Test
+  public void keywordExistsInFileAndIsRemoved() throws Exception {
+    pushFactory
+        .create(
+            admin.newIdent(), clone, "Subject", "file.txt", "" + "blah \n" + "secr3t\n" + "blah")
+        .to("refs/heads/master")
+        .assertOkStatus();
+    pushConfig(
+        Joiner.on("\n").join("[plugin \"uploadvalidator\"]", "    blockedKeywordPattern = secr3t"));
+    pushFactory
+        .create(admin.newIdent(), clone, "Subject", "file.txt", "" + "blah \n" + "blah\n")
+        .to("refs/heads/master")
+        .assertOkStatus();
+  }
+
+  @Test
+  public void keywordExistsInFileAndSameLineIsModified() throws Exception {
+    pushFactory
+        .create(
+            admin.newIdent(),
+            clone,
+            "Subject",
+            "file.txt",
+            "" + "blah \n" + "secr3t\n" + "blah" + "")
+        .to("refs/heads/master")
+        .assertOkStatus();
+    pushConfig(
+        Joiner.on("\n").join("[plugin \"uploadvalidator\"]", "    blockedKeywordPattern = secr3t"));
+    // This could be further improved using intra-line diffs
+    pushFactory
+        .create(
+            admin.newIdent(),
+            clone,
+            "Subject",
+            "file.txt",
+            "" + "blah \n" + "secr3t foobar\n" + "blah" + "")
+        .to("refs/heads/master")
+        .assertErrorStatus("blocked keywords");
+  }
+
+  @Test
+  public void keywordExistsInOldAndFileIsDeleted() throws Exception {
+    pushFactory
+        .create(
+            admin.newIdent(),
+            clone,
+            "Subject",
+            "file.txt",
+            "" + "blah \n" + "secr3t\n" + "blah" + "")
+        .to("refs/heads/master")
+        .assertOkStatus();
+    pushConfig(
+        Joiner.on("\n").join("[plugin \"uploadvalidator\"]", "    blockedKeywordPattern = secr3t"));
+    pushFactory
+        .create(admin.newIdent(), clone, "Subject", "foo.txt", "blah")
+        .rmFile("file.txt")
+        .to("refs/heads/master")
+        .assertOkStatus();
+  }
 }