diff --git a/packages/vitest/src/node/reporters/tap.ts b/packages/vitest/src/node/reporters/tap.ts
index 0800d9ad5c14..53096f523d14 100644
--- a/packages/vitest/src/node/reporters/tap.ts
+++ b/packages/vitest/src/node/reporters/tap.ts
@@ -1,5 +1,5 @@
 import type { Task } from '@vitest/runner'
-import type { ParsedStack } from '@vitest/utils'
+import type { ErrorWithDiff, ParsedStack } from '@vitest/utils'
 import type { Vitest } from '../../node'
 import type { Reporter } from '../../types/reporter'
 import { parseErrorStacktrace } from '../../utils/source-map'
@@ -36,9 +36,10 @@ export class TapReporter implements Reporter {
       return ''
   }
 
-  private logErrorDetails(error: Error, stack?: ParsedStack) {
-    this.logger.log(`name: ${yamlString(error.name)}`)
-    this.logger.log(`message: ${yamlString(error.message)}`)
+  private logErrorDetails(error: ErrorWithDiff, stack?: ParsedStack) {
+    const errorName = error.name || error.nameStr || 'Unknown Error'
+    this.logger.log(`name: ${yamlString(String(errorName))}`)
+    this.logger.log(`message: ${yamlString(String(error.message))}`)
 
     if (stack) {
       // For compatibility with tap-mocha-reporter
diff --git a/test/reporters/fixtures/custom-error/basic.test.ts b/test/reporters/fixtures/custom-error/basic.test.ts
new file mode 100644
index 000000000000..41220e57f830
--- /dev/null
+++ b/test/reporters/fixtures/custom-error/basic.test.ts
@@ -0,0 +1,17 @@
+import { test } from 'vitest';
+
+test('no name object', () => {
+  throw { noName: 'hi' };
+});
+
+test('string', () => {
+  throw "hi";
+});
+
+test('number', () => {
+  throw 1234;
+});
+
+test('number name object', () => {
+  throw { name: 1234 };
+});
diff --git a/test/reporters/fixtures/custom-error/vitest.config.ts b/test/reporters/fixtures/custom-error/vitest.config.ts
new file mode 100644
index 000000000000..abed6b2116e1
--- /dev/null
+++ b/test/reporters/fixtures/custom-error/vitest.config.ts
@@ -0,0 +1,3 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({})
diff --git a/test/reporters/tests/tap.test.ts b/test/reporters/tests/tap.test.ts
new file mode 100644
index 000000000000..51cdf518ca16
--- /dev/null
+++ b/test/reporters/tests/tap.test.ts
@@ -0,0 +1,37 @@
+import { expect, test } from 'vitest'
+import { runVitest } from '../../test-utils'
+
+test('handle custom error without name', async () => {
+  let { stdout, stderr } = await runVitest({ reporters: 'tap-flat', root: './fixtures/custom-error' })
+  stdout = stdout.replaceAll(/time=(\S*)/g, 'time=[...]') // strip non-deterministic output
+  expect(stdout).toMatchInlineSnapshot(`
+    "TAP version 13
+    1..4
+    not ok 1 - basic.test.ts > no name object # time=[...]
+        ---
+        error:
+            name: "Unknown Error"
+            message: "undefined"
+        ...
+    not ok 2 - basic.test.ts > string # time=[...]
+        ---
+        error:
+            name: "Unknown Error"
+            message: "hi"
+        ...
+    not ok 3 - basic.test.ts > number # time=[...]
+        ---
+        error:
+            name: "Unknown Error"
+            message: "1234"
+        ...
+    not ok 4 - basic.test.ts > number name object # time=[...]
+        ---
+        error:
+            name: "1234"
+            message: "undefined"
+        ...
+    "
+  `)
+  expect(stderr).toBe('')
+})