diff --git a/extensions/ql-vscode/CHANGELOG.md b/extensions/ql-vscode/CHANGELOG.md
index f481fe913e8..2202d07710f 100644
--- a/extensions/ql-vscode/CHANGELOG.md
+++ b/extensions/ql-vscode/CHANGELOG.md
@@ -6,6 +6,7 @@
 - Fix bug to ensure error messages have complete stack trace in message logs. [#2425](https://github.com/github/vscode-codeql/pull/2425)
 - Fix bug where the `CodeQL: Compare Query` command did not work for comparing quick-eval queries. [#2422](https://github.com/github/vscode-codeql/pull/2422)
 - Update text of copy and export buttons in variant analysis results view to clarify that they only copy/export the selected/filtered results. [#2427](https://github.com/github/vscode-codeql/pull/2427)
+- Add warning when using unsupported CodeQL CLI version. [#2428](https://github.com/github/vscode-codeql/pull/2428)
 
 ## 1.8.4 - 3 May 2023
 
diff --git a/extensions/ql-vscode/src/codeql-cli/cli.ts b/extensions/ql-vscode/src/codeql-cli/cli.ts
index d5ef116d465..969ba374b00 100644
--- a/extensions/ql-vscode/src/codeql-cli/cli.ts
+++ b/extensions/ql-vscode/src/codeql-cli/cli.ts
@@ -1737,6 +1737,10 @@ export function shouldDebugCliServer() {
 }
 
 export class CliVersionConstraint {
+  // The oldest version of the CLI that we support. This is used to determine
+  // whether to show a warning about the CLI being too old on startup.
+  public static OLDEST_SUPPORTED_CLI_VERSION = new SemVer("2.7.6");
+
   /**
    * CLI version where building QLX packs for remote queries is supported.
    * (The options were _accepted_ by a few earlier versions, but only from
diff --git a/extensions/ql-vscode/src/extension.ts b/extensions/ql-vscode/src/extension.ts
index aad6940f523..888884bdd5d 100644
--- a/extensions/ql-vscode/src/extension.ts
+++ b/extensions/ql-vscode/src/extension.ts
@@ -24,7 +24,7 @@ import {
   activate as archiveFilesystemProvider_activate,
   zipArchiveScheme,
 } from "./common/vscode/archive-filesystem-provider";
-import { CodeQLCliServer } from "./codeql-cli/cli";
+import { CliVersionConstraint, CodeQLCliServer } from "./codeql-cli/cli";
 import {
   CliConfigListener,
   DistributionConfigListener,
@@ -408,6 +408,28 @@ export async function activate(
     codeQlExtension.cliServer.addVersionChangedListener((ver) => {
       telemetryListener.cliVersion = ver;
     });
+
+    let unsupportedWarningShown = false;
+    codeQlExtension.cliServer.addVersionChangedListener((ver) => {
+      if (!ver) {
+        return;
+      }
+
+      if (unsupportedWarningShown) {
+        return;
+      }
+
+      if (CliVersionConstraint.OLDEST_SUPPORTED_CLI_VERSION.compare(ver) < 0) {
+        return;
+      }
+
+      void showAndLogWarningMessage(
+        `You are using an unsupported version of the CodeQL CLI (${ver}). ` +
+          `The minimum supported version is ${CliVersionConstraint.OLDEST_SUPPORTED_CLI_VERSION}. ` +
+          `Please upgrade to a newer version of the CodeQL CLI.`,
+      );
+      unsupportedWarningShown = true;
+    });
   }
 
   return codeQlExtension;