The aim of this study was to examine both positive and negative aspects of relationship quality in relation to condom use. Sexually active young women aged 14-18 years (n = 111; 34% non-white) were recruited from community clinics and schools in the Midwest USA and provided data via an online survey. The number of unprotected sex acts in the past month with the most recent male partner was regressed on relationship quality with that partner, adjusting for demographics and other characteristics. Negative relationship quality was associated with a greater number of unprotected sex acts among women reporting a low level of positive relationship quality and among women taking hormonal/IUD contraception. Positive relationship quality was associated with unprotected sex among women who reported multiple partners in the past month. Both positive and negative aspects of relationship quality may confer risk for unprotected sex. This risk appears to be modified by patterns of contraceptive use and other sexual behaviours. Health professionals and sexual health educators may be more effective in promoting condom use if they ask questions about both positive and negative aspects of young people's relationship quality and tailor their conversations based on the responses received.