Relationships influence sexual risk and maternal-child health. Few studies have assessed relationship dissolution and its association with sexually transmitted diseases (STD) among adolescent parents. Our study aimed to describe relationship dissolution among 295 parenting and non-parenting adolescents over an 18-month period and how it related to STD incidence. Results showed that nonparenting adolescents in a relationship with someone other than their baby's father were more likely to have a relationship dissolution over an 18-month period compared to those in a relationship with the baby's father (OR = 1.69, P < .05). Parenting adolescents who ended their relationship with their baby's father were 3 times more likely to get an STD over the course of the study compared to parenting adolescents who remained with their baby's father (39% vs. 13%). Comparatively, nonparenting adolescents who ended their relationship were only 1.4 times more likely to get an STD compared to non-parenting adolescents who remained with their partner (44% vs. 32%). Our results suggest that prevention programs that incorporate male partners and components that strengthen relationship skills may reduce HIV/STD risk and help adolescents adapt during times of transition such as parenthood.