Incarceration is strongly associated with HIV infection and may contribute to viral transmission by disrupting stable partnerships and promoting high-risk partnerships. We investigated incarceration and STI/HIV-related partnerships among a community-based sample recruited for a sexual behavior interview while frequenting venues where people meet sexual partners in a North Carolina city (N = 373). Men reporting incarceration in the past 12 months were more likely than men without recent incarceration to experience multiple new sexual partnerships (unadjusted prevalence ratio [PR] 1.8, 95% confidence interval [CI]: 1.1-3.1) and transactional sex defined as trading sex for money, goods, or services (unadjusted PR: 4.0, 95% CI: 2.3-7.1) in the past 4 weeks. Likewise, women who were ever incarcerated were more likely than never-incarcerated women to experience recent multiple new partnerships (unadjusted PR: 3.1, 95% CI: 1.8-5.4) and transactional sex (unadjusted PR: 5.3, 95% CI: 2.6-10.9). Sexual partnership in the past 12 months with someone who had ever been incarcerated versus with partners with no known incarceration history was associated with recent multiple new partnerships (men: unadjusted PR 2.0, 95% CI 1.4-2.9, women: unadjusted PR 4.8, 95% CI 2.3-10.1) and transactional sex (men: unadjusted PR 3.3, 95% CI 1.7-6.6, women: unadjusted PR 6.1, 95% CI 2.4-15.4). Adjustment for demographic and socioeconomic variables had minimal effect on estimates. However, the strong overlap between incarceration, partner incarceration, and substance abuse had substantial effects in multivariable models. Correctional-facility and community-based HIV prevention, with substance abuse treatment, should reach currently and formerly incarcerated individuals and their sexual partners.