"So sorry to disappoint, but no home wreckers or secret flings going on here," she captioned a photo of herself with Galecki. "Me and @sanctionedjohnnygalecki are just the best of buds - Leonard and Penny will just have to suffice!!!"
Cuoco and Galecki play Penny and Leonard on CBS series The Big Bang Theory, and secretly dated from 2008 to 2010. The actress said she and her co-star "moved on" romantically, but remain "best friends" on Watch What Happens Live in September.
The National Enquirer had sparked the rumors by claiming Cuoco "never stopped having feelings for Galecki" in an article last week. The actress and Sweeting were married less than two years, and will reportedly honor their prenuptial agreement.
The Big Bang Theory returned for a ninth season in September, and kicked off the new episodes with Leonard and Penny's wedding. The series co-stars Jim Parsons as Sheldon, Simon Helberg as Howard and Kunal Nayyar as Raj, and airs Mondays at 8 p.m. ET.