Gyllenhaal began dating Witherspoon after meeting the actress on the set of Rendition. The two split amicably in late 2009, with Witherspoon starting a relationship with future husband Jim Toth soon after. The couple tied the knot this past weekend after dating for little over a year.
According to Us Weekly, Gyllenhaal spent the night bowling with friends while Witherspoon married Toth, and appeared in high spirits.
"They looked really into it and seemed really relaxed," a witness said. "As the game progressed, the guys started high-fiving each other; at one point Jake did what looked like a little dance after bowling a spare."
Gyllenhaal has only dated singer Taylor Swift since splitting from Witherspoon. The pair began dating in mid-October and broke up just before Christmas, with the Prince Of Persia star reportedly ending the relationship due to the large amount of press that the couple received.
Gyllenhaal can be seen next in Source Code, opening in UK and US cinemas on April 1.