The actress, who won the 'Best Actress' award for her role in Silver Linings Playbook, was being interviewed for ABC's Good Morning America when the 75-year-old acting legend snuck up to congratulate her, causing her to almost jump out of her seat.
Nicholson, who can be seen mopping his brow thoroughly before coming up, told the 22-year-old that she had done "such a beautiful job" in the film, before apologising to the interviewer as Lawrence joked: "Yeah, you're being really rude."
When Nicholson told Lawrence that she looked like an old girlfriend of his, she replied with the faux flirty question: "Oh really, do I look like a new girlfriend?"
"I thought about it," Nicholson replied. Lawrence laughed, but as he ventured away she gasped, "Oh my God", and buried her head in her hands.
Seconds later Nicholson appeared over her shoulder, wearing sunglasses and said: "I'll be waiting," causing her to jump once again.
"I need a rear view mirror," a flustered Lawrence declared, revealing that she had never met Nicholson before he came over.
"I know Jennifer Garner though," she said, waving at the actress and blowing a kiss to her. "Yeah, this is my life now, hey Jack, hey Jennifer, how are you?"
Lawrence was also seen by GMA hugging 'Best Supporting Actress' winner Anne Hathaway and 'bumping Oscars' with her.
The Hunger Games star has been the main talking point of this year's Academy Awards after she fell up the stairs on the way to collect her prize and was photographed 'giving the finger' with her Oscar still in hand.
Oscars 2013 - photo gallery: