The pregnancy rumours were sparked when Keibler was photographed with a possible baby bump while at Clooney's Italian vacation home.
A friend of Keibler has now clarified to TMZ that the rumours are "100% false".
Keibler appeared to disprove the reports by being photographed drinking an apparently alcoholic cocktail at a dinner with Clooney.
The couple were first linked in August 2011 and went public a month later.
Earlier today, it was reported that Clooney will produce Meryl Streep and Julia Roberts's upcoming dark comedy August: Osage County.
Watch George Clooney in a trailer for The Descendants below: