DeKay, who plays FBI Agent Peter Burke on the USA series, will appear in the eighth episode of Chuck as Kieran Ryker, Sarah's stoic former CIA handler who makes her confront her past. (If Agent Burke is busy at Buy More, who is going to make sure Neal stays out of trouble back in New York?)
DeKay, 48, joins previously announced final-season guest stars Mark Hamill, Carrie Anne Moss and Stan Lee, among others. He is also set to direct an episode of White Collar when the show returns for the second half of Season 3 this winter.
Chuck's final season kicks off on Friday, Oct. 28 at 8/7c on NBC.