diff --git a/java/com/google/gerrit/pgm/Init.java b/java/com/google/gerrit/pgm/Init.java
index 799377c..3593d8a 100644
--- a/java/com/google/gerrit/pgm/Init.java
+++ b/java/com/google/gerrit/pgm/Init.java
@@ -30,6 +30,7 @@
 import com.google.gerrit.pgm.util.ErrorLogFile;
 import com.google.gerrit.server.config.GerritServerConfigModule;
 import com.google.gerrit.server.config.SitePath;
+import com.google.gerrit.server.index.GerritIndexStatus;
 import com.google.gerrit.server.ioutil.HostPlatform;
 import com.google.gerrit.server.securestore.SecureStoreClassName;
 import com.google.gerrit.server.util.ReplicaUtil;
@@ -60,9 +61,6 @@
   @Option(name = "--no-auto-start", usage = "Don't automatically start daemon after init")
   private boolean noAutoStart;
 
-  @Option(name = "--no-reindex", usage = "Don't automatically reindex any entities")
-  private boolean noReindex;
-
   @Option(name = "--skip-plugins", usage = "Don't install plugins")
   private boolean skipPlugins;
 
@@ -91,6 +89,8 @@
 
   @Inject Browser browser;
 
+  private boolean projectsIndexExists;
+
   public Init() {
     super(new WarDistribution(), null);
   }
@@ -103,6 +103,7 @@
 
   @Override
   protected boolean beforeInit(SiteInit init) throws Exception {
+    projectsIndexExists = new GerritIndexStatus(init.site).exists(ProjectSchemaDefinitions.NAME);
     ErrorLogFile.errorOnlyConsole();
 
     if (!skipPlugins) {
@@ -145,7 +146,7 @@
         });
     modules.add(new GerritServerConfigModule());
     Guice.createInjector(modules).injectMembers(this);
-    if (!ReplicaUtil.isReplica(run.flags.cfg)) {
+    if (!ReplicaUtil.isReplica(run.flags.cfg) && !projectsIndexExists) {
       reindexProjects();
     }
     start(run);
@@ -260,9 +261,6 @@
   }
 
   private void reindexProjects() throws Exception {
-    if (noReindex) {
-      return;
-    }
     // Reindex all projects, so that we bootstrap the project index for new installations
     List<String> reindexArgs =
         ImmutableList.of(
diff --git a/java/com/google/gerrit/server/index/GerritIndexStatus.java b/java/com/google/gerrit/server/index/GerritIndexStatus.java
index 6d59100..9f0622e 100644
--- a/java/com/google/gerrit/server/index/GerritIndexStatus.java
+++ b/java/com/google/gerrit/server/index/GerritIndexStatus.java
@@ -48,6 +48,10 @@
     return cfg.getBoolean(SECTION, indexDirName(indexName, version), KEY_READY, false);
   }
 
+  public boolean exists(String indexName) {
+    return cfg.getSubsections(SECTION).stream().anyMatch(n -> n.startsWith(indexName));
+  }
+
   public void save() throws IOException {
     cfg.save();
   }
diff --git a/javatests/com/google/gerrit/acceptance/pgm/InitIT.java b/javatests/com/google/gerrit/acceptance/pgm/InitIT.java
index e48088e..4caee64 100644
--- a/javatests/com/google/gerrit/acceptance/pgm/InitIT.java
+++ b/javatests/com/google/gerrit/acceptance/pgm/InitIT.java
@@ -26,7 +26,16 @@
 import com.google.gerrit.index.project.ProjectIndexCollection;
 import com.google.gerrit.server.config.AllProjectsName;
 import com.google.gerrit.server.config.AllUsersName;
+import java.io.IOException;
+import java.nio.file.FileVisitOption;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.Instant;
+import java.util.Comparator;
 import java.util.Optional;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import org.eclipse.jgit.util.FS;
 import org.junit.Test;
 
 @NoHttpd
@@ -34,7 +43,7 @@
 
   @Test
   public void indexesAllProjectsAndAllUsers() throws Exception {
-    runGerrit("init", "-d", sitePaths.site_path.toString(), "--show-stack-trace");
+    initSite();
     try (ServerContext ctx = startServer()) {
       ProjectIndexCollection projectIndex =
           ctx.getInjector().getInstance(ProjectIndexCollection.class);
@@ -48,4 +57,52 @@
       assertThat(allUsersData).isPresent();
     }
   }
+
+  @Test
+  public void initDoesNotReindexProjectsOnExistingSites() throws Exception {
+    initSite();
+
+    // Simulate a projects indexes files modified in the past by 3 seconds
+    Optional<Instant> projectsLastModified =
+        getProjectsIndexLastModified(sitePaths.index_dir).map(t -> t.minusSeconds(3));
+    assertThat(projectsLastModified).isPresent();
+    setProjectsIndexLastModifiedInThePast(sitePaths.index_dir, projectsLastModified.get());
+
+    initSite();
+    Optional<Instant> projectsLastModifiedAfterInit =
+        getProjectsIndexLastModified(sitePaths.index_dir);
+
+    // Verify that projects index files haven't been updated
+    assertThat(projectsLastModified).isEqualTo(projectsLastModifiedAfterInit);
+  }
+
+  private void initSite() throws Exception {
+    runGerrit("init", "-d", sitePaths.site_path.toString(), "--show-stack-trace");
+  }
+
+  private void setProjectsIndexLastModifiedInThePast(Path indexDir, Instant time)
+      throws IOException {
+    for (Path path : getAllProjectsIndexFiles(indexDir).collect(Collectors.toList())) {
+      FS.DETECTED.setLastModified(path, time);
+    }
+  }
+
+  private Optional<Instant> getProjectsIndexLastModified(Path indexDir) throws IOException {
+    return getAllProjectsIndexFiles(indexDir)
+        .map(FS.DETECTED::lastModifiedInstant)
+        .max(Comparator.comparingLong(Instant::toEpochMilli));
+  }
+
+  private Stream<Path> getAllProjectsIndexFiles(Path indexDir) throws IOException {
+    Optional<Path> projectsPath =
+        Files.walk(indexDir, 1)
+            .filter(Files::isDirectory)
+            .filter(p -> p.getFileName().toString().startsWith("projects_"))
+            .findFirst();
+    if (!projectsPath.isPresent()) {
+      return Stream.empty();
+    }
+
+    return Files.walk(projectsPath.get(), 1, FileVisitOption.FOLLOW_LINKS);
+  }
 }