diff --git a/src/plugin/customParseFormat/index.js b/src/plugin/customParseFormat/index.js
index c7082833c..61f4cfb1c 100644
--- a/src/plugin/customParseFormat/index.js
+++ b/src/plugin/customParseFormat/index.js
@@ -1,6 +1,6 @@
 import { u } from '../localizedFormat/utils'
 
-const formattingTokens = /(\[[^[]*\])|([-_:/.,()\s]+)|(A|a|Q|YYYY|YY?|ww?|MM?M?M?|Do|DD?|hh?|HH?|mm?|ss?|S{1,3}|z|ZZ?)/g
+const formattingTokens = /(\[[^[]*\])|([-_:/.,()\s]+)|(A|a|Q|YYYY|YY?|ww?|WW?|MM?M?M?|Do|DD?|hh?|HH?|mm?|ss?|S{1,3}|z|ZZ?)/g
 
 const match1 = /\d/ // 0 - 9
 const match2 = /\d\d/ // 00 - 99
@@ -100,6 +100,8 @@ const expressions = {
   }],
   w: [match1to2, addInput('week')],
   ww: [match2, addInput('week')],
+  W: [match1to2, addInput('week')],
+  WW: [match2, addInput('week')],
   M: [match1to2, addInput('month')],
   MM: [match2, addInput('month')],
   MMM: [matchWord, function (input) {
diff --git a/test/plugin/customParseFormat.test.js b/test/plugin/customParseFormat.test.js
index fb4030176..d3237041e 100644
--- a/test/plugin/customParseFormat.test.js
+++ b/test/plugin/customParseFormat.test.js
@@ -8,10 +8,12 @@ import customParseFormat from '../../src/plugin/customParseFormat'
 import advancedFormat from '../../src/plugin/advancedFormat'
 import localizedFormats from '../../src/plugin/localizedFormat'
 import weekOfYear from '../../src/plugin/weekOfYear'
+import isoWeek from '../../src/plugin/isoWeek'
 
 dayjs.extend(customParseFormat)
 dayjs.extend(localizedFormats)
 dayjs.extend(weekOfYear) // test parse w, ww
+dayjs.extend(isoWeek) // test parse W, WW
 
 beforeEach(() => {
   MockDate.set(new Date())
@@ -452,11 +454,17 @@ it('parse Q, [Q]', () => {
   expect(dayjs(input4, format).valueOf()).toBe(moment(input4, format).valueOf())
 })
 
-it('parse w, ww', () => {
+it('parse w, ww, W, WW', () => {
   const input = '2024-w1'
   const format1 = 'YYYY-[w]w'
   expect(dayjs(input, format1).format(format1)).toBe(input)
   const input2 = '2024-w32'
   const format2 = 'YYYY-[w]ww'
-  expect(dayjs(input2, format2).format(format1)).toBe(input2)
+  expect(dayjs(input2, format2).format(format2)).toBe(input2)
+  const input3 = '2024-w1'
+  const format3 = 'YYYY-[w]W'
+  expect(dayjs(input3, format3).format(format3)).toBe(input3)
+  const input4 = '2024-w33'
+  const format4 = 'YYYY-[w]WW'
+  expect(dayjs(input4, format4).format(format4)).toBe(input4)
 })