Yes they are. In fact, they've been dating for almost 3 years! They started in August of 2006, on the break between Season 1 and Season 1.5 of Psych. :)
He has been dating Psych co-star Maggie Lawson since 2006. He will guest host along side with Dule 爬坡道, 小山 the January 25th edition of 美国职业摔跤 Monday Night Raw