Internalized sex work stigma among cisgender female sex workers (FSW) is produced within contexts of social marginalization and associated with a range of ill-effects, including psychological distress, and lower rates of healthcare-seeking. This study seeks to uncover latent domains of the new Internalized Sex Work Stigma Scale (ISWSS) using data from 367 FSW in Baltimore, Maryland, USA. The sample was 56% white with high substance use (82% smoked crack cocaine, 58% injected any drug). The average ISWSS score was 34.8 (s.d. = 5.8, possible range: 12-48) and internal consistency was high (0.82). Confirmatory factor analysis revealed four subscales: worthlessness, guilt and shame, stigma acceptance, and sex work illegitimacy. Internal consistency of subscales was high (0.69-0.90); the scale also demonstrated construct validity with depression and agency. In bivariate logistic regressions, higher ISWSS, worthlessness, shame and guilt, and acceptance scores predicted higher odds of rushing client negotiations due to police. In unadjusted multinomial regressions, feeling respected by police predicted lower ISWSS, worthlessness, guilt and shame, acceptance, and illegitimacy scores. Identified factors are congruent with existing literature about how FSW manage sex work-specific stigma. Understanding the unique dimensions and impacts of internalized sex work stigma can inform interventions and policy to reduce morbidities experienced by FSW.