The 51-year-old actor, who was previously said to be moving on from former flame Scarlett Johansson, was seen enjoying dinner in Miami with 26-year-old Shannon Costello, People reports.
Penn was first spotted with Costello in July, but was misidentified as Stacey Koplin at the time. Costello met the I Am Sam star in 2009.
Penn was first linked romantically to Johansson earlier this year after the two attended Reese Witherspoon's wedding together.
However, the actor ultimately chose to break the relationship off as he was allegedly not ready for a "serious" relationship.
Penn was previously married to actress Robin Wright as well as Madonna.
Watch Sean Penn in the trailer for The Tree of Life below: