Also in attendance were their children, Apple, 11, and Moses, 9, reported People magazine.
"Gwyneth and Chris arrived separately. At the party, they were friendly, hung out with their kids and also mingled. Guests were treated to a barbecue and all seemed to enjoy the party," a source said.
It is not the first holiday that Paltrow, 42, and Martin, 38, have spent together since finalising their divorce in April. They spent this Mother's Day together as well.
Other celebrities who attended Silver's Memorial Day party included Kate Hudson, Courteney Cox and fiance Johnny McDaid, Tobey Maguire and Jennifer Meyer, Minnie Driver, Kate Beckinsale, Diane Kruger, January Jones and Bella Thorne.