diff --git a/messages/sdr.md b/messages/sdr.md
index 32d31dec9..5b71679d9 100644
--- a/messages/sdr.md
+++ b/messages/sdr.md
@@ -22,6 +22,10 @@ Could not find parent type for %s (%s)
 
 Component conversion failed: %s
 
+# error_invalid_test_level
+
+TestLevel cannot be '%s' unless API version is %s or later
+
 # error_merge_metadata_target_unsupported
 
 Merge convert for metadata target format currently unsupported
diff --git a/src/client/metadataApiDeploy.ts b/src/client/metadataApiDeploy.ts
index 1e2bbb2bf..2d3ca0b6f 100644
--- a/src/client/metadataApiDeploy.ts
+++ b/src/client/metadataApiDeploy.ts
@@ -116,6 +116,7 @@ export class MetadataApiDeploy extends MetadataTransfer<
   public constructor(options: MetadataApiDeployOptions) {
     super(options);
     options.apiOptions = { ...MetadataApiDeploy.DEFAULT_OPTIONS.apiOptions, ...options.apiOptions };
+    validateOptions(options);
     this.options = Object.assign({}, options);
     this.isRestDeploy = !!options.apiOptions?.rest;
     this.registry = options.registry ?? new RegistryAccess();
@@ -524,6 +525,17 @@ const buildFileResponsesFromComponentSet =
     }
     return fileResponses;
   };
+
+const validateOptions = (options: MetadataApiDeployOptions): void => {
+  const runningRelevantTestsOnly = options.apiOptions?.testLevel === 'RunRelevantTests';
+  const beforeApiV66 = options.apiVersion && Number(options.apiVersion) < 66.0;
+  if (runningRelevantTestsOnly && beforeApiV66) {
+    throw new SfError(
+      messages.getMessage('error_invalid_test_level', ['RunRelevantTests', '66.0']),
+      'InvalidTestLevelSelection'
+    );
+  }
+};
 /**
  * register a listener to `scopedPreDeploy`
  */
diff --git a/src/client/types.ts b/src/client/types.ts
index 5da3ece36..dacbfd0c3 100644
--- a/src/client/types.ts
+++ b/src/client/types.ts
@@ -364,7 +364,7 @@ export type MetadataApiDeployOptions = {
   runAllTests?: boolean;
   runTests?: string[];
   singlePackage?: boolean;
-  testLevel?: 'NoTestRun' | 'RunSpecifiedTests' | 'RunLocalTests' | 'RunAllTestsInOrg';
+  testLevel?: 'NoTestRun' | 'RunSpecifiedTests' | 'RunLocalTests' | 'RunAllTestsInOrg' | 'RunRelevantTests';
   /**
    * Set to true to use the REST API for deploying.
    */
diff --git a/test/client/metadataApiDeploy.test.ts b/test/client/metadataApiDeploy.test.ts
index c8da492d7..ace098fd6 100644
--- a/test/client/metadataApiDeploy.test.ts
+++ b/test/client/metadataApiDeploy.test.ts
@@ -1256,6 +1256,30 @@ describe('MetadataApiDeploy', () => {
       expect(mdOpts.zipPath).to.equal('foo/myZip.zip');
     });
 
+    it('should disallow "RunRelevantTests" for API versions <66.0', () => {
+      const testCases = ['8.0', '10.0', '60.0', '65.0'];
+      const constructorError = {
+        name: 'InvalidTestLevelSelection',
+        message: messages.getMessage('error_invalid_test_level', ['RunRelevantTests', '66.0']),
+      };
+      try {
+        testCases.forEach((v) => {
+          new MetadataApiDeploy({
+            usernameOrConnection: 'testing',
+            apiOptions: {
+              testLevel: 'RunRelevantTests',
+            },
+            apiVersion: v,
+          });
+          assert.fail(`Should have thrown an error for API version ${v}`);
+        });
+      } catch (e) {
+        assert(e instanceof Error);
+        expect(e.name).to.equal(constructorError.name);
+        expect(e.message).to.equal(constructorError.message);
+      }
+    });
+
     it('should allow mdapi path', () => {
       const mdApiDeploy = new MetadataApiDeploy({
         usernameOrConnection: 'testing',