The efficacy of parent-based HIV prevention interventions is dependent on the retention of parents in clinical trials. In a sample of urban African American mothers (N = 525), we investigated potential predictors affecting the likelihood of their retention in a longitudinal study testing an HIV/STI risk-reduction intervention designed to reduce their and their adolescent son’s HIV risk behavior compared with a health-promotion control intervention. Mothers’ sociodemographic and family characteristics and self-reported number of male sexual partners were measured along with their retention for intervention sessions and follow-up data collection sessions. Sociodemographics (e.g., employment status, educational attainment), family characteristics (e.g., household size), multiple male sexual partners, and intervention type were not associated with the mothers’ retention rates. Analysis over multiple intervention and post-intervention data-collection sessions revealed that mothers’ employment status predicted reduced retention for intervention booster sessions and post-intervention data collection. Implications for effectively tailoring interventions and further investigations are discussed.