The Golden Globe winner was not on hand when it was announced she won best actress at the ceremony Saturday, and her co-star, Jacki Weaver, accepted on her behalf, the New York Daily News reported.
"I am going to accept this award on behalf of Jennifer," said Weaver, who is nominated for a best supporting actress Oscar. "She really wishes she could be here, but she is very ill."
Weaver told the audience at the Soho House in Hollywood that Lawrence, 22, was suffering from pneumonia, which has caused her to be too sick to attend several awards ceremonies recently, the newspaper said.
Weaver read Lawrence's acceptance speech, which expressed her gratitude and her interest in traveling to Australia one day to visit the Sydney Opera House.
Lawrence is also a front-runner for the best actress category at the Academy Awards ceremony on Feb. 24.
Pregnant Mila Kunis wins 'Best Villain' at MTV Movie Awards
Pistorius testifies he didn't consciously pull trigger when he shot girlfriend