The two-time Emmy winner, 80, will play the estranged con man/father of Juliet (Maggie Lawson).
As TVGuide.com first reported, viewers will meet Frank when he attempts to mend his broken relationship with Juliet, with a little help from Shawn (James Roday) and Gus (Dulé Hill). However, the chance to pull off a dream con will make Frank's decision to give up his life of crime more complicated.
Shatner, best known as Capt. Kirk in the original Star Trek TV series and seven subsequent Trek films, most recently starred on the CBS sitcom $#*! My Dad Says. He won two Emmys for his portrayal of Denny Crane, first on The Practice and then on its spin-off Boston Legal. Shatner also hosts an interview show on the Biography Channel, Shatner's Raw Nerve.
Psych returns in the fall on USA.