Onlookers say the 40-year-old beauty did her best to entice the British actor while they were enjoying the LACMA Art + Film Gala in Los Angeles – but he reportedly wasn’t interested.
"She was pretty obvious," a witness told Us Weekly.
"Cam was seated next to Rob at dinner. She was touching his arm, doing her big Cameron laugh at everything he said and trying really hard. He was polite, but not having it."
Cameron has previously dated big Hollywood stars, including Jared Leto and Justin Timberlake.
However, her high-profile romances have not worked out so far, with ex-lover Justin marrying Jessica Biel last month.
A fling with Robert certainly seems off the cards as he rekindled his relationship with Twilight co-star Kristen in September, after it emerged she had an affair with married director Rupert Sanders.
The couple were spotted looking smitten at a Prince concert last month.
"They were inseparable - kissing passionately," a concertgoer revealed.
"It was like watching one of their movies! Rob was grinning the entire time."
