Background Research among street-based female sex workers (FSWs) has documented many harms caused by police. One harm that has received little attention is that of police as clients. We examined this interaction in a 12-month longitudinal cohort study of street-based FSWs in Baltimore, MD. Methods We explored longitudinal bivariate and multivariate associations between having police clients and independent variables that focused on sexually transmitted infections (STIs), as well as demographic, structural, substance use, police interaction, and violence-related factors. Results Mean participant age was 35.8 years, 65.9% were White, and more than half (53.3%) had less than a high school education. Most (70.3%) used heroin daily, and 24.8% reported having police as clients over the study period. In a multivariate model, factors independently associated with recent police clients were recent arrest (adjusted odds ratio [aOR], 1.76; 95% confidence interval [CI], 1.03-2.99; P = 0.037), coerced or forced sex by police (aOR, 4.47; 95% CI, 1.79-11.12; P = 0.001), higher number of egregious police practices experienced (aOR, 1.77; 95% CI, 1.38-2.29; P < 0.001), and prevalent STI infection (aOR, 2.43; 95% CI, 1.46-4.04; P = 0.001). Conclusions The study uniquely documents both the frequency with which street-based FSWs take police as clients and the role of egregious police practices and prevalent STIs in association with police as clients. Results indicate the police-as-client association as a form of "everyday violence," which both normalizes and legitimizes police power and structural violence. Alongside the urgent need for decriminalization of sex work and STI prevention programs tailored for this complex population, prompt investigation and harsher penalties for police officers who engage in sex with FSW could help shift police culture away from abuse.