The 51-year-old Hollywood actor and the Czech model have been seen on a series of dates in recent weeks, reported Daily Mail online.
They were most recently seen at U2 frontman Bono's birthday party at The Spotted Pig in the West Village of New York.
The sighting of the pair comes just weeks after Nemcova called off her wedding to Jamie Belman.
The formerly engaged couple had dated for eight months before Belman popped the question in December 2010. But it was announced in April this year that they were no longer together.
Penn's divorce from wife of 14 years, Robin Wright, was finally finalised in July 2010 after several years being on and off.
He had dated Nemcova during one of his separations from his wife and were first linked together during award season in 2008.
He went on to date Hollywood star Scarlett Johansson soon after her split from actor Ryan Reynolds.
