Research has shown that greater stress responses predict worse sleep and that the quality of one’s current romantic relationship predicts one’s sleep. Despite these established links, research has not examined connections between ongoing patterns of interpersonal experiences and competencies (relationship effectiveness) and stress exposure on sleep. Participants in the Minnesota Longitudinal Study of Risk and Adaptation (MLSRA) completed measures assessing relationship effectiveness and stress exposure at ages 23 and 32 years, as well as sleep quality/duration at age 37 years. Analyses demonstrate that relationship effectiveness at age 23 years positively predicts sleep quality—but not sleep duration—at age 37 years via reduced stress exposure at age 32 years. These findings highlight the effects of relationship effectiveness and stress exposure across early to middle adulthood on sleep.