Abstract Background Despite increasing rates of incarceration and sexually transmitted infections (STIs) among women globally, STI epidemiological data for this vulnerable at-risk population is limited. We therefore characterized patterns of STI symptoms and explored covariates and drivers of STI symptoms among incarcerated women in Peru. Methods Among 249 incarcerated women surveyed on substance use, depression, sexual behavior, STI symptoms and violence, univariate and bivariate analysis informed a latent profile analysis (LPA) and logistic regression assessing for syndemic associations between violence, substance use, and STI symptoms. Results Most participants were Peruvian (93.5%), in their late 30s (median=37; range:18-70 years), sentenced to < 5 years (86.6%) and had completed high school (78.7%). 36.9 had ≥2 STI; A minority were pregnant (2.6%), had children residing with them in prison (7.2%); symptoms. The LPA model with the best fit revealed the largest (39%) group with a ‘syndemic’ profile involving co-occurrence of multiple STI symptoms, substance use, and experiences of interpersonal violence (IPV); 86.6% of this latent class were <50 years old. The substance use and violence ‘syndemic’ profile was associated significantly higher likelihood of having multiple STI symptoms (2+ symptoms: PR = 1.88 (95% CI 1.18, 2.99) or 3+ symptoms PR = 2.55 (95% CI 1.32, 4.93). Conclusions and Recommendations The syndemic of younger incarcerated women with substance use and IPV with STI symptoms portends a group at substantially higher risk for HIV and given the structured setting of prisons, should be routinely screened for and treated for STIs. Moreover, these settings can and should screen for and address substance use and IPV and intervene before these women are released to community settings to not only improve individual but public health needs. Key messages • In line with syndemic theory, incarcerated women presenting with multiple STI symptoms (≥2) were more likely to be engaged in substance use (illicit drug use and/or alcohol) and experience violence. • Post-hoc analysis also revealed the rate of substance use was higher among women who engaged in commercial sex work (CSW) pre-incarceration compared to those who were not engaged in CSW.