Dakota Johnson's rep says the actress is not expecting with Chris Martin.
Johnson's rep said the bash was in honor of the "Fifty Shades" star's birthday, which fell Oct. 4. The party took place Sunday at Martin's house.
TMZ had reported Johnson's pregnancy after photos showed pink and blue balloons floating over Martin's house.
Johnson's parents, Melanie Griffith and Don Johnson, Julia Roberts and Sean Penn were among the guests at the event.
Griffith told reporters in May she approves of Johnson dating the 41-year-old Coldplay singer.
"I adore him!" the actress said. "But she is very private about her life and I respect that."
"I'm not going to talk about it, but I am very happy," she said.
Martin was previously married to actress Gwyneth Paltrow, who wed producer Brad Falchuk in September.
Martin and Paltrow are parents to 14-year-old daughter Apple and 12-year-old son Moses.