Clijsters and American Bob Bryan were defeated by Brazilian Bruno Soares and Russia’s Ekaterina Makarova 6-2, 3-6, 12-10 in a second-round match on the Grandstand stadium.
“It was an honour to be part of this lifestyle and this sport. I started when I was four and had so many dreams come true,” said Clijsters.
“But life goes on. Tonight was one of the reasons why I wanted to play mixed doubles. Tennis will always be a part of my life and I will always follow it.
“I have won many beautiful things and have so many friendships but now I have a new chapter with my family.”
Clijsters, who won three US Open singles titles, said earlier this year that this would be her final season and the US Open her farewell event.
She was ousted from the singles tournament in the second round by Britain’s Laura Robson and in her first women’s doubles match alongside compatriot Kirsten Flipkens.
Her final shot as a tennis player was a netted forehand which gave Soares and Makarova the victory.
Serena on the move
In the women’s singles, three-time champion Serena Williams (right) went level with sister Venus on 61 US Open career wins when she coasted into the fourth round. Olympic and Wimbledon champion Williams won eight games in succession to claim a 6-4, 6-0 win over Russia’s world 42 Ekaterina Makarova.