Stuart Dunn, 27, was detained about 11 a.m. Friday when police from the Los Angeles police were called to a gym where he had allegedly shown up three days in a row trying to come in contact with the actress.
Dunn was detained for a mental health evaluation, but no charges were filed.
Police said Dunn was under a court order to stay away from the 29-year-old actress after being arrested in January for attempting to break into her West Hollywood apartment.
Last week, a judge held a hearing looking into the possibility that Dunn violated his probation.
Kunis got her big break on the TV series "That '70s Show" and recently starred in the films "Black Swan" and "Friends with Benefits."