Infidelity is a major factor in causing marital dissolution and dissatisfaction in North America. Similarities in personality traits influence the desire for a monogamous relationship commitment. The present study examined differences between cheaters and non-cheaters on Goldberg’s (1990) “Big-Five Personality Factors”: Extroversion, Agreeableness, Conscientiousness, Emotional Stability, and Intellect-Openness. One hundred and four participants volunteered to answer a questionnaire on personality traits about themselves and their monogamous partners. A total of 45 males and 59 females rated themselves and an equal number of partners on the traits (n = 208). Results revealed statistically significant differences between cheaters and non-cheaters on the five-factor model. Differences were also found between both of the group’s perceptions of themselves and their monogamous partners on these factors.