The effectiveness of visual realism of virtual characters in engaging users and eliciting affective responses has been an open question. We empirically evaluated the effects of realistic vs. non-realistic rendering of virtual humans on the emotional response of participants in a medical virtual reality system that was designed to educate users to recognize the signs and symptoms of patient deterioration. In a between-subjects experiment protocol, participants interacted with one of three different appearances of a virtual patient, namely realistic, non-realistic cartoon-shaded and charcoal-sketch like conditions. Emotional impact of the rendering conditions was measured via a combination of subjective and objective metrics.