The televised match was due to take place on Sunday evening but will now be rearranged for a later date.
West Ham had seen their final game of 2021, away to Chelsea, called off due to positive tests inside the Blues dressing room.
Manchester City’s game against Reading and Arsenal versus Brighton were also called off last month. No other WSL games this weekend have currently been postponed.
A club statement read: “West Ham United Women can confirm that Sunday’s Barclays FA Women's Super League fixture against Manchester United Women has been postponed.
“The decision was agreed between both teams and the FA due to a number of suspected positive Covid-19 cases amongst our players and staff.
“Following the postponement of the fixture, West Ham United Women can confirm that all general admission tickets purchased for the match will remain valid for the rescheduled fixture.”
