Heavy episodic drinking (HED) is a major health problem for young adults. Rates of HED have remained consistently high among young adults for the past two decades. Though research has identified various intrapersonal, interpersonal, and environmental contributors to HED, the majority of research focuses on intrapersonal factors. As such, more research is needed to test the role that specific interpersonal relationships play in perpetuating HED. This study tests the partner influence hypothesis that suggests partners in romantic relationships influence one another's HED over time. A sample of 208 young, nonmarried, heterosexual dating couples completed HED measures at baseline and again 28 days later. Actor–partner interdependence modeling revealed significant actor effects, demonstrating stability in HED within each partner over time. Results also showed significant partner effects where HED in both young men and women in dating relationships positively influenced their partners' future HED over a relatively short time frame. Patterns in the results suggest both women and men are more affected by their own than by their partner's prior level of HED. Nonetheless, small partner effects were present for both women and men. Results support the partner influence hypothesis and suggest HED is a self-propagating behavior sustained, in part, by a pattern of interpersonal influence. These results highlight the importance of considering both intrapersonal and interpersonal factors when implementing prevention and intervention programs for young adults' HED.