This mixed methods study looked into whether gender and adult attachment style influence one’s tendency to commit dating infidelity. Infidelity has three types: physical infidelity, emotional infidelity, and combined infidelity. We constructed and administered the adult attachment style test, and the infidelity tendency and type scale to 262 participants who were not married but had at least been in a committed relationship. After conducting two-way ANOVA tests, it was found that males had the higher propensity to commit all three types of infidelity. Moreover, those with avoidant adult attachment styles were most likely to commit all types of infidelity compared with those with secure and anxious ambivalent attachment styles. We used thematic analysis for the qualitative part of the study to explore other social factors that contribute to one’s dating infidelity tendency. We interviewed six participants and found two major themes that may influence the person’s dating infidelity tendency: perception of infidelity and relationship with the dating partner.