diff --git a/src/lib/isISO8601.js b/src/lib/isISO8601.js
index 6eea9ae27..d8809a671 100644
--- a/src/lib/isISO8601.js
+++ b/src/lib/isISO8601.js
@@ -11,7 +11,7 @@ const isValidDate = (str) => {
   // this check is meant to catch invalid dates
   // like 2009-02-31
   // first check for ordinal dates
-  const ordinalMatch = str.match(/^(\d{4})-?(\d{3})([ T]{1}\.*|$)/);
+  const ordinalMatch = str.match(/^[\+-]?(\d{4})-?(\d{3})([ T]{1}\.*|$)/);
   if (ordinalMatch) {
     const oYear = Number(ordinalMatch[1]);
     const oDay = Number(ordinalMatch[2]);
diff --git a/test/validators.test.js b/test/validators.test.js
index 98d2a12ff..61003c5bd 100644
--- a/test/validators.test.js
+++ b/test/validators.test.js
@@ -12443,6 +12443,9 @@ describe('Validators', () => {
         '2009-222',
         '2020-366',
         '2400-366',
+        '+2009-145',
+        '+2009-130',
+        '-2009-145',
       ],
       invalid: [
         '2010-02-30',