OBJECTIVE: To determine how weekly text messages and small incentives impact HIV knowledge and frequency of HIV testing among Latinx sexual minority men (LSMM) and transgender women (LTGW). DESIGN: Prospectively randomized participants into 2 intervention arms compared with a nonrandomized comparison group. SETTING: Bienestar, a primarily Latinx focused HIV service provider located across Los Angeles County. SUBJECTS, PARTICIPANTS: Two hundred eighteen participants self-identifying as LSMM or LTGW, HIV negative, having regular mobile phone access, ≥18 years, and fluent in English or Spanish. INTERVENTION: The "information only" (IO) group received text messages with HIV prevention information. The "information plus" (IP) group additionally could win incentives by answering weekly quiz questions correctly and testing for HIV once every 3 months. We followed participants for 12 months. MAIN OUTCOME MEASURE(S): HIV knowledge and frequency of HIV testing. RESULTS: We found no effect on HIV knowledge in the IO group but a statistically significant improvement in the IP group (79.2%-88.1%; P = 0.007). The frequency of HIV testing was higher in both intervention groups relative to the comparison group: On average, 22.0% of IO participants and 24.9% of IP participants tested at a Bienestar site within a given 3-month period, compared with 13.0% in the comparison group. This represents unadjusted relative risk ratios of 1.69 for the IO group (95% CI: 1.25 to 2.1; P < 0.01) and 1.91 for the IP group (95% CI: 1.51 to 2.31; P < 0.01), respectively. CONCLUSIONS: This study demonstrates that a simple, low-cost intervention may help increase HIV testing frequency among LSMM and LTGW, 2 groups at high HIV risk.