Motherwell organised two pitch inspections following heavy rain but the match was called off less than two hours before kick-off.
The Lanarkshire club said on their Twitter feed: "Tonight's match with Dundee Utd has been postponed due to a small area on the East Stand side which is waterlogged.
"The club would like to apologise for any inconvenience the call off causes. We tried to give it every chance but it just came up short."
Referee Stephen Finnie made the decision at about 6pm with the ball unable to bounce properly on the affected area.
Finnie told BBC Scotland: "There was one problem area when I was doing the first inspection.
"At that time, there was heavy rain and nowhere for the water to go.
"I relayed that back to the SPL and given the weather forecast for the rain going off, they decided to do another one at quarter to six."
But the affected area was still not playable and the game was called off despite the rain going off.
Finnie said: "It's a danger to the players. The ball was just not bouncing at all. There was no option.
"We can't predict the weather in Scotland. You have to make a decision at a certain time, as advised by the SPL.
"You give the game every chance but we took the team over and showed them what the ball was doing and there was no argument at all."