Sexual concurrency may increase risk for HIV/STIs among youth. Attitudes about gender roles, including power balances within sexual partnerships, could be a driver. We examined this association among Baltimore youth (N = 352), aged 15–24. Data were collected from February, 2011 to May, 2013. We examined whether index concurrency in male-reported partnerships (N = 221) and sex partner’s concurrency in female-reported partnerships (N = 241) were associated with youth’s attitudes towards relationship power. Males with more equitable beliefs about power were less likely to report index concurrency. Females with more equitable beliefs were more likely to report sex partner’s concurrency. The relationship was significant in main and casual partnerships among females and main partnerships among males. The strongest associations were detected among middle-socioeconomic status (SES) males and low-SES and African American females. Implementing interventions that recognize the complex relationship between socioeconomic context, partner dynamics, gender, and sexual behavior is an important step towards reducing HIV/STI risk among youth.