Research suggests that women’s sexual psychology and behavior change across the ovulatory cycle, but very little is known about how fluctuations in estradiol and progesterone – two hormones that systematically vary across the ovulatory cycle – affect romantic relationship dynamics. We present the first dyadic study to assess daily hormonal fluctuations and personal and relationship well-being from both partners’ perspectives. Specifically, we recruited women who were not using hormonal contraception and their partners for a 15-day diary study. Participants collected daily urine samples to assess estradiol, progesterone, and testosterone, and they responded to daily questions about their relationship. Results revealed that increases in estradiol negatively affected women’s relationship evaluations. Men perceived these changes, which in turn, affected men’s well-being. The present findings highlight the importance of women’s hormonal fluctuations in shaping relationship dynamics and provide, for the first time, information about how such fluctuations affect male partners.