Men who have sex with men (MSM) are at increased risk for HIV infection in India, particularly those who engage in transactional sex with other men (i.e., male sex workers; MSW). Despite the need, HIV prevention efforts for Indian MSW are lacking. As in other settings, MSW in India increasingly rely on the use of mobile phones for sex work solicitation. Integrating mobile phone technology into an HIV prevention intervention for Indian MSW may mitigate some of the challenges associated with face-to face approaches, such as implementation, lack of anonymity, and time consumption, while at the same time proving to be both feasible and useful. This is a pilot randomized controlled trial to examine participant acceptability, feasibility of study procedures, and preliminary efficacy for reducing sexual risk for HIV. MSW (N = 100) were equally randomized to: (1) a behavioral HIV prevention intervention integrating in-person and mobile phone delivered HIV risk reduction counseling, and daily, personalized text or voice messages as motivating "cognitive restructuring" cues for reducing condomless anal sex (CAS); or (2) a standard of care (SOC) comparison condition. Both groups received HIV counseling and testing at baseline and 6-months, and completed ACASI-based, behavioral and psychosocial assessments at baseline, 3, and 6 months. Mixed-effects regression procedures specifying a Poisson distribution and log link with a random intercept and slope for month of follow-up was estimated to assess the intervention effect on the primary outcomes: (1) CAS acts with male clients who paid them for sex, and (2) CAS acts with male non-paying sexual partners-both outcomes assessed over the past month. The intervention was both feasible (98% retention at 6-months) and acceptable (>96% of all intervention sessions attended); all intervention participants rated the intervention as "acceptable" or "very acceptable." A reduction in the reported number of CAS acts with male clients who paid them for sex in the past month was seen in both study conditions. MSW in the intervention condition reported a faster rate of decline in the number of CAS acts with male clients in the past month from the baseline to both the 3-month (B = -1.20; 95% CI -1.68, -0.73; p < 0.0001) and 6-month (B = -2.44; 95% CI -3.35, -1.53; p < 0.00001) assessment visits compared to the SOC condition. Post-hoc contrasts indicated that, at 3 months, participants in the intervention condition reported 1.43 (SD = 0.29) CAS acts with male clients in the past month compared to 4.85 (SD = 0.87) in the control condition (p = 0.0003). Furthermore, at 6 months, the intervention condition participants reported 0.24 (SD = 0.09) CAS acts with male clients in the past month compared to 2.79 (SD = 0.79) in the control condition (p < 0.0001). Findings are encouraging and provide evidence of feasibility and acceptability, and demonstrate initial efficacy (for reducing sexual risk for HIV) of a behavioral HIV prevention intervention for Indian MSW that combines daily, personalized text or voice messages with mobile phone-delivered sexual risk reduction counseling and skills building. Future testing of the intervention in a fully powered randomized controlled efficacy trial is warranted.