diff --git a/messages/alias.set.md b/messages/alias.set.md
index 507899ff..3c9ca822 100644
--- a/messages/alias.set.md
+++ b/messages/alias.set.md
@@ -4,7 +4,7 @@ Set one or more aliases on your local computer.
 
 # description
 
-Aliases are user-defined short names that make it easier to use the CLI. For example, users often set an alias for a scratch org usernames because they're long and unintuitive.  Check the --help of a CLI command to determine where you can use an alias.
+Aliases are user-defined short names that make it easier to use the CLI. For example, users often set an alias for a scratch org usernames because they're long and unintuitive. Check the --help of a CLI command to determine where you can use an alias.
 
 You can associate an alias with only one value at a time. If you set an alias multiple times, the alias points to the most recent value. Aliases are global; after you set an alias, you can use it in any Salesforce DX project on your computer.
 
@@ -35,3 +35,9 @@ You must provide one or more aliases to set. Use the --help flag to see examples
 # error.ValueRequired
 
 You must provide a value when setting an alias. Use `sf alias unset my-alias-name` to remove existing aliases.
+
+# warning.spaceAlias
+
+The alias "%s" includes a space. We recommend aliases without spaces.
+
+If you decide to keep "%s", you must wrap it in double quotes when using it in any CLI command.  For example:  sf project deploy start --target-org "my scratch". 
diff --git a/src/commands/alias/set.ts b/src/commands/alias/set.ts
index 5d1f7851..b69e25be 100644
--- a/src/commands/alias/set.ts
+++ b/src/commands/alias/set.ts
@@ -34,6 +34,9 @@ export default class AliasSet extends AliasCommand<AliasResults> {
     const results = await Promise.all(
       Object.entries(parsed).map(async ([alias, value]) => {
         try {
+          if (alias.includes(' ')) {
+            this.warn(messages.getMessage('warning.spaceAlias', [alias, alias]));
+          }
           // to support plugin-settings in sfdx, which allowed setting an alias to undefined, when that happens we'll unset the alias
           // which is what the user wants
           if (!value) {
diff --git a/test/commands/alias/set.nut.ts b/test/commands/alias/set.nut.ts
index ca350fa6..6f76c003 100644
--- a/test/commands/alias/set.nut.ts
+++ b/test/commands/alias/set.nut.ts
@@ -66,6 +66,18 @@ describe('alias set NUTs', () => {
       expect(result).to.deep.equal([{ alias: 'foo', success: true, value: 'alias with spaces' }]);
     });
 
+    it('alias set with spaces in alias (produces warning)', () => {
+      const value = 'bar';
+      const result = execCmd(`alias set "foo with space"=${value} --json`, {
+        ensureExitCode: 0,
+      }).jsonOutput;
+
+      expect(result?.result).to.deep.equal([{ alias: 'foo with space', success: true, value }]);
+      expect(result?.warnings).to.deep.equal([
+        messages.getMessage('warning.spaceAlias', ['foo with space', 'foo with space']),
+      ]);
+    });
+
     it('allow setting a single alias without an equal sign', () => {
       const result = execCmd('alias set theKey theValue --json', {
         ensureExitCode: 0,