A.J. Cook worked with an actor.
Andrea Joy `` A. J. '' Cook ( born July 22 , 1978 ) is a Canadian actress known for her role as Supervisory Special Agent Jennifer `` JJ '' Jareau in the CBS crime drama Criminal Minds . Criminal Minds . The show has an ensemble cast that has had many cast member changes since its inception . Thomas Gibson , Shemar Moore , Matthew Gray Gubler , A. J. Cook , and Kirsten Vangsness are the only actors to have appeared in every season .