Objective: Sexual intercourse is a dyadic activity, and intentions to engage in safe sex vary across partners. Because pregnant and newly parenting adolescents and young adults are at high risk for sexually transmitted infections (STIs), it is important to understand sexual decision-making in this population. Method: This cross-sectional study examined how participants’ own risk behavior and their partners’ risk behavior influence perceptions of partner risk, and the impact of risk perceptions on condom use intentions and monogamy intentions in 296 pregnant adolescent and young adult couples (MAgeFemale = 18.71 years; MAgeMale = 21.33 years). Results: Participants’ behavior and their partners’ behavior both related to increased perceptions of partner risk. Male participants’ perceptions were more strongly influenced by female partners’ behavior than participants’ own behavior. Perceiving a partner as having a history of more risk behaviors trended toward a negative relationship with condom use intentions and monogamy intentions. For females, more previous sex partners related negatively to condom use intentions and positively to monogamy intentions. Having a male partner with more previous sex partners related positively to condom use intentions and monogamy intentions. Conclusions: Perceptions of partner risk did not significantly relate to condom use intentions and monogamy intentions, however, trends suggest that risk perception could reflect similarity bias and ongoing risk engagement. Differences in partner perception by gender suggest that females may communicate more openly about risks. Interventions to reduce STI transmission in couples should work to interrupt trajectories of risky behavior and enhance risk communication.