diff --git a/plugins/woocommerce-blocks/package.json b/plugins/woocommerce-blocks/package.json
index cd63f8a5ca4..45f4c6d706b 100644
--- a/plugins/woocommerce-blocks/package.json
+++ b/plugins/woocommerce-blocks/package.json
@@ -288,7 +288,7 @@
 		"fast-deep-equal": "^3.1.3",
 		"fast-sort": "^3.4.0",
 		"html-react-parser": "3.0.4",
-		"postcode-validator": "3.8.15",
+		"postcode-validator": "3.9.2",
 		"preact": "^10.19.3",
 		"prop-types": "^15.8.1",
 		"react-number-format": "4.9.3",
diff --git a/plugins/woocommerce-blocks/packages/checkout/utils/validation/is-postcode.ts b/plugins/woocommerce-blocks/packages/checkout/utils/validation/is-postcode.ts
index ec2ca97a1c3..2ab21d238b9 100644
--- a/plugins/woocommerce-blocks/packages/checkout/utils/validation/is-postcode.ts
+++ b/plugins/woocommerce-blocks/packages/checkout/utils/validation/is-postcode.ts
@@ -13,6 +13,7 @@ const CUSTOM_REGEXES = new Map< string, RegExp >( [
 	[ 'JP', /^([0-9]{3})([-]?)([0-9]{4})$/ ],
 	[ 'KH', /^[0-9]{6}$/ ], // Cambodia (6-digit postal code).
 	[ 'LI', /^(94[8-9][0-9])$/ ],
+	[ 'MN', /^[0-9]{5}(-[0-9]{4})?$/ ], // Mongolia (5-digit postal code or 5-digit postal code followed by a hyphen and 4-digit postal code).
 	[ 'NI', /^[1-9]{1}[0-9]{4}$/ ], // Nicaragua (5-digit postal code)
 	[ 'NL', /^([1-9][0-9]{3})(\s?)(?!SA|SD|SS)[A-Z]{2}$/i ],
 	[ 'SI', /^([1-9][0-9]{3})$/ ],
diff --git a/plugins/woocommerce/changelog/50279-fix-mongolia-postcode-5 b/plugins/woocommerce/changelog/50279-fix-mongolia-postcode-5
new file mode 100644
index 00000000000..b6f3ac11940
--- /dev/null
+++ b/plugins/woocommerce/changelog/50279-fix-mongolia-postcode-5
@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Adjust Mongolia postcode validation to be 5 digits or 5 digits followed by 4 digits.
\ No newline at end of file
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 2a972c8f247..296a64d656a 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -4025,8 +4025,8 @@ importers:
         specifier: 3.0.4
         version: 3.0.4(react@18.3.1)
       postcode-validator:
-        specifier: 3.8.15
-        version: 3.8.15
+        specifier: 3.9.2
+        version: 3.9.2
       preact:
         specifier: ^10.19.3
         version: 10.19.3
@@ -20623,8 +20623,8 @@ packages:
     resolution: {integrity: sha512-xTgYBc3fuo7Yt7JbiuFxSYGToMoz8fLoE6TC9Wx1P/u+LfeThMOAqmuyECnlBaaJb+u1m9hHiXUEtwW4OzfUJg==}
     engines: {node: '>=0.10.0'}
 
-  postcode-validator@3.8.15:
-    resolution: {integrity: sha512-B2oeZ4E9D7JBHk0GEo0lv9aqHGd6vv+VsWoTG6Jt0tMtc5RUzSXOSQixBZgAAn4A/Dbajp8GbwzMtUkkyYw2Ig==}
+  postcode-validator@3.9.2:
+    resolution: {integrity: sha512-C+oaXif+z+mAN1EWDZG/EM2dnrUxRQR0gpMq8VeLSZwHuT3Bqo4hR3+k7OaEevPl0VK/7W27JwEQb24CbdtzuQ==}
 
   postcss-calc@7.0.5:
     resolution: {integrity: sha512-1tKHutbGtLtEZF6PT4JSihCHfIVldU72mZ8SdZHIYriIZ9fh9k9aWSppaT8rHsyI3dX+KSR+W+Ix9BMY3AODrg==}
@@ -56933,7 +56933,7 @@ snapshots:
 
   posix-character-classes@0.1.1: {}
 
-  postcode-validator@3.8.15: {}
+  postcode-validator@3.9.2: {}
 
   postcss-calc@7.0.5:
     dependencies: