diff --git a/packages/vitest/src/node/cli.ts b/packages/vitest/src/node/cli.ts
index 187cfd48a163..2feb8fa61201 100644
--- a/packages/vitest/src/node/cli.ts
+++ b/packages/vitest/src/node/cli.ts
@@ -22,6 +22,7 @@ cli
   .option('--silent', 'silent console output from tests')
   .option('--isolate', 'isolate environment for each test file (default: true)')
   .option('--reporter <name>', 'reporter')
+  .option('--outputTruncateLength <length>', 'diff output length')
   .option('--outputFile <filename>', 'write test results to a file when the --reporter=json option is also specified')
   .option('--coverage', 'use c8 for coverage')
   .option('--run', 'do not watch')
diff --git a/packages/vitest/src/node/diff.ts b/packages/vitest/src/node/diff.ts
index 0d81599da3fb..b1d325d8b897 100644
--- a/packages/vitest/src/node/diff.ts
+++ b/packages/vitest/src/node/diff.ts
@@ -2,8 +2,8 @@ import c from 'picocolors'
 import * as diff from 'diff'
 import cliTruncate from 'cli-truncate'
 
-export function formatLine(line: string) {
-  return cliTruncate(line, (process.stdout.columns || 80) - 4)
+export function formatLine(line: string, outputTruncateLength?: number) {
+  return cliTruncate(line, (outputTruncateLength ?? (process.stdout.columns || 80)) - 4)
 }
 
 /**
@@ -15,7 +15,7 @@ export function formatLine(line: string) {
 * @return {string} The diff.
 */
 
-export function unifiedDiff(actual: string, expected: string) {
+export function unifiedDiff(actual: string, expected: string, outputTruncateLength?: number) {
   if (actual === expected)
     return ''
 
@@ -54,16 +54,16 @@ export function unifiedDiff(actual: string, expected: string) {
 
   let formatted = lines.map((line: string) => {
     if (line[0] === '-') {
-      line = formatLine(line.slice(1))
+      line = formatLine(line.slice(1), outputTruncateLength)
       if (isCompact)
         return c.green(line)
-      return c.green(`- ${formatLine(line)}`)
+      return c.green(`- ${formatLine(line, outputTruncateLength)}`)
     }
     if (line[0] === '+') {
-      line = formatLine(line.slice(1))
+      line = formatLine(line.slice(1), outputTruncateLength)
       if (isCompact)
         return c.red(line)
-      return c.red(`+ ${formatLine(line)}`)
+      return c.red(`+ ${formatLine(line, outputTruncateLength)}`)
     }
     if (line.match(/@@/))
       return '--'
diff --git a/packages/vitest/src/node/error.ts b/packages/vitest/src/node/error.ts
index 56f46d97a779..cc3daa6d1d70 100644
--- a/packages/vitest/src/node/error.ts
+++ b/packages/vitest/src/node/error.ts
@@ -40,7 +40,7 @@ export async function printError(error: unknown, ctx: Vitest) {
   handleImportOutsideModuleError(e.stack || e.stackStr || '', ctx)
 
   if (e.showDiff)
-    displayDiff(e.actual, e.expected, ctx.console)
+    displayDiff(e.actual, e.expected, ctx.console, ctx.config.outputTruncateLength)
 }
 
 const esmErrors = [
@@ -79,8 +79,8 @@ function handleImportOutsideModuleError(stack: string, ctx: Vitest) {
 }\n`)))
 }
 
-function displayDiff(actual: string, expected: string, console: Console) {
-  console.error(c.gray(unifiedDiff(actual, expected)) + '\n')
+function displayDiff(actual: string, expected: string, console: Console, outputTruncateLength?: number) {
+  console.error(c.gray(unifiedDiff(actual, expected, outputTruncateLength)) + '\n')
 }
 
 function printErrorMessage(error: ErrorWithDiff, console: Console) {
diff --git a/packages/vitest/src/types/config.ts b/packages/vitest/src/types/config.ts
index 7a8aed92b205..39c4cf5c71ce 100644
--- a/packages/vitest/src/types/config.ts
+++ b/packages/vitest/src/types/config.ts
@@ -137,6 +137,11 @@ export interface InlineConfig {
    */
   reporters?: Arrayable<BuiltinReporters | Reporter>
 
+  /**
+   * diff output length
+   */
+  outputTruncateLength?: number
+
   /**
    * Write test results to a file when the --reporter=json option is also specified
    */