Fifty-two non-treatment-seeking methamphetamine-using men who have sex with men were enrolled in Project Tech Support, an open-label pilot study to evaluate whether exposure to theory-based [social support theory (SST), social cognitive theory (SCT), and health belief model (HBM)] text messages could promote reductions in HIV sexual risk behaviors and/or methamphetamine use. Multivariable analyses revealed that increased relative exposure to HBM or SCT (vs. SST) text messages was associated with significant reductions in the number of HIV serodiscordant unprotected (i.e., without a condom) anal sex partners, engagement in sex for money and/or drugs, and frequency of recent methamphetamine use; additionally, increased relative exposure to HBM (vs. SCT or SST) messages was uniquely associated with reductions in the overall number of non-primary anal sex partners (all p ≤ 0.05, two-tailed). Pilot data demonstrated that text messages based on the principles of HBM and SCT reduced sentinel HIV risk and drug use behaviors in active methamphetamine users.