Herpes simplex virus (HSV) infection is a well-known trigger mechanism for both erythema multiforme (EM) and psoriasis. While HSV-related EM and psoriasis are not uncommon, simultaneous development of both disorders following HSV infection is relatively rare. We report on a patient who simultaneously developed both EM and a guttate psoriasis within 16 days of an HSV infection. The major differences in the pathophysiological mechanisms by which these dermatoses are triggered are discussed.