Humor has been identified as an important factor in the establishment of relationships. This study explores the use of humor in mental health therapy and how clients’ preferences for humor impact an evaluation of the therapy session. Forty-eight individuals currently receiving mental health therapy were examined along with the use of three forms of humor: positive, negative, and instrumental. There was a significant relationship between a preference for negative humor and session evaluation scores in which the more negative humor preferred, the lower the session ratings. Although not significant, other trends were noted between self-enhancing humor and session depth, aggressive humor and session depth, and affiliative humor and positivity. Gender differences and preference for humor were also examined with men reporting higher value on negative humor than women and women reporting greater post-session arousal than men. These findings are discussed in terms of the need for further research to consider factors that may have influenced the present study’s results.