diff --git a/packages/cli-repl/src/arg-parser.spec.ts b/packages/cli-repl/src/arg-parser.spec.ts
index fa83121417..72bb532dd4 100644
--- a/packages/cli-repl/src/arg-parser.spec.ts
+++ b/packages/cli-repl/src/arg-parser.spec.ts
@@ -322,12 +322,12 @@ describe('arg-parser', () => {
         context('when providing --gssapiHostName', () => {
           const argv = [ ...baseArgv, uri, '--gssapiHostName', 'example.com' ];
 
-          it('throws an error since it is not yet supported', () => {
+          it('throws an error since it is not supported', () => {
             try {
               parseCliArgs(argv);
             } catch (e: any) {
               expect(e).to.be.instanceOf(MongoshUnimplementedError);
-              expect(e.message).to.include('Argument --gssapiHostName is not yet supported in mongosh');
+              expect(e.message).to.include('Argument --gssapiHostName is not supported in mongosh');
               return;
             }
             expect.fail('Expected error');
@@ -488,15 +488,15 @@ describe('arg-parser', () => {
           });
         });
 
-        context('when providing --tlsFIPSMode', () => {
-          const argv = [ ...baseArgv, uri, '--tlsFIPSMode' ];
+        context('when providing --sslFIPSMode', () => {
+          const argv = [ ...baseArgv, uri, '--sslFIPSMode' ];
 
-          it('throws an error since it is not yet supported', () => {
+          it('throws an error since it is not supported', () => {
             try {
               parseCliArgs(argv);
             } catch (e: any) {
               expect(e).to.be.instanceOf(MongoshUnimplementedError);
-              expect(e.message).to.include('Argument --tlsFIPSMode is not yet supported in mongosh');
+              expect(e.message).to.include('Argument --sslFIPSMode is not supported in mongosh');
               return;
             }
             expect.fail('Expected error');
diff --git a/packages/cli-repl/src/arg-parser.ts b/packages/cli-repl/src/arg-parser.ts
index af5791258a..7c2d81c6ae 100644
--- a/packages/cli-repl/src/arg-parser.ts
+++ b/packages/cli-repl/src/arg-parser.ts
@@ -115,7 +115,6 @@ const DEPRECATED_ARGS_WITH_REPLACEMENT: Record<string, keyof CliOptions> = {
  */
 const UNSUPPORTED_ARGS: Readonly<string[]> = [
   'sslFIPSMode',
-  'tlsFIPSMode',
   'gssapiHostName'
 ];
 
@@ -188,7 +187,7 @@ export function verifyCliArguments(args: any /* CliOptions */): string[] {
   for (const unsupported of UNSUPPORTED_ARGS) {
     if (unsupported in args) {
       throw new MongoshUnimplementedError(
-        `Argument --${unsupported} is not yet supported in mongosh`,
+        `Argument --${unsupported} is not supported in mongosh`,
         CommonErrors.InvalidArgument
       );
     }
diff --git a/packages/cli-repl/src/run.ts b/packages/cli-repl/src/run.ts
index 30309b95f7..e2150a9aaa 100644
--- a/packages/cli-repl/src/run.ts
+++ b/packages/cli-repl/src/run.ts
@@ -1,3 +1,13 @@
+let fipsError: Error | undefined;
+if (process.argv.includes('--tlsFIPSMode')) {
+  // FIPS mode should be enabled before we run any other code, including any dependencies.
+  try {
+    require('crypto').setFips(1);
+  } catch (err: any) {
+    fipsError = err;
+  }
+}
+
 import { CliRepl, parseCliArgs, runSmokeTests, USAGE, buildInfo } from './index';
 import { getStoragePaths, getGlobalConfigPaths } from './config-directory';
 import { getCSFLELibraryPaths } from './csfle-library-paths';
@@ -8,6 +18,7 @@ import { runMain } from 'module';
 import readline from 'readline';
 import askcharacter from 'askcharacter';
 import stream from 'stream';
+import crypto from 'crypto';
 
 // eslint-disable-next-line complexity, @typescript-eslint/no-floating-promises
 (async() => {
@@ -29,6 +40,31 @@ import stream from 'stream';
 
     const { version } = require('../package.json');
 
+    if (options.tlsFIPSMode) {
+      if (!fipsError && !crypto.getFips()) {
+        // We can end up here if somebody used an unsual spelling of
+        // --tlsFIPSMode that our arg parser recognizes, but not the
+        // early check above, e.g. --tls-FIPS-mode.
+        // We should also just generally check that FIPS mode is
+        // actually enabled.
+        fipsError = new Error('FIPS mode not enabled despite requested');
+      }
+      if (fipsError) {
+        // Adjust the error message depending on whether this mongosh binary
+        // potentially can support FIPS or not.
+        if (process.config.variables.node_shared_openssl) {
+          console.error('Could not enable FIPS mode. Please ensure that your system OpenSSL installation');
+          console.error('supports FIPS, and see the mongosh FIPS documentation for more information.');
+        } else {
+          console.error('Could not enable FIPS mode. This mongosh installation does not appear to');
+          console.error('support FIPS. Please see the mongosh FIPS documentation for more information.');
+        }
+        console.error('Error details:');
+        console.error(fipsError);
+        process.exit(1);
+      }
+    }
+
     if (options.help) {
       // eslint-disable-next-line no-console
       console.log(USAGE);
diff --git a/packages/cli-repl/test/e2e.spec.ts b/packages/cli-repl/test/e2e.spec.ts
index 6a1917d906..5e4b5fe04a 100644
--- a/packages/cli-repl/test/e2e.spec.ts
+++ b/packages/cli-repl/test/e2e.spec.ts
@@ -156,6 +156,20 @@ describe('e2e', function() {
         shell.assertContainsOutput('233');
       });
     });
+    it('accepts a --tlsFIPSMode argument', async() => {
+      shell = TestShell.start({
+        args: [ '--nodb', '--tlsFIPSMode' ]
+      });
+      const result = await shell.waitForPromptOrExit();
+      // Whether this worked depends on the environment the test is running in.
+      // We check both possibilities.
+      if (result.state === 'exit') {
+        shell.assertContainsOutput('Could not enable FIPS mode');
+        expect(result.exitCode).to.equal(1);
+      } else {
+        expect(await shell.executeLine('[crypto.getFips()]')).to.include('[1]');
+      }
+    });
   });
 
   describe('set db', () => {