Lesbian, gay, bisexual, and other sexual minority (LGB+) girls are more likely than heterosexual girls to be pregnant during adolescence. Nonetheless, LGB+ inclusive pregnancy prevention programming is lacking. Between January 2017 and January 2018, 948, 14 to 18 year-old cisgender LGB+ girls were enrolled in a national randomized controlled trial. Girls were assigned either to Girl2Girl or an attention-matched control group. They were recruited via social media and enrolled over the telephone. The 5-month intervention consisted of a 7-week program (4-12 text messages sent daily) and a 1-week booster delivered 12 weeks later. Longitudinal models of protected sex events had a negative binomial distribution and a log link function. Longitudinal models examining use of birth control assumed a Bernoulli distribution of the outcome variable and a logit link function. Models adjusted for baseline rate of the outcome, age, and a time-varying indicator of sexual experience. Girl2Girl participants had higher rates of protected penile-vaginal sex events over time compared with controls. Girl2Girl participants also were more likely than control participants to report use of birth control other than condoms. Models of abstinence and pregnancy rates did not suggest statistically significant group differences across time. However, effect sizes were in the small to medium range and point estimates favored Girl2Girl versus control in both cases. Girl2Girl is associated with sustained pregnancy preventive behaviors for LGB+ girls through 12 months postintervention. Text messaging could be considered as a viable method to increase access to sexual health programming to adolescents nationally.