Methamphetamine use is highly prevalent among gay, bisexual, and other men who have sex with men (MSM) in the United States and has been associated with condomless anal intercourse (CAI), a common route of HIV infection. Text messaging is a very low-cost method of delivery for intervention content. This paper presents a cost-effectiveness analysis of a randomized controlled trial testing three nested methods of text message delivery designed to reduce methamphetamine use and HIV sexual risk behaviors among MSM (Project Tech Support2). From March 2014 to January 2016, 286 non-treatment seeking methamphetamine-using MSM were randomized into one of three study arms: 1) Interactive text message conversations with Peer Health Educators, plus five daily automated, unidirectional theory-based messages, plus a weekly self-monitoring text message assessment (TXT-PHE; n = 94); or, 2) Five daily automated, unidirectional theory-based messages plus a weekly self-monitoring text message assessment (TXT-Auto; n = 99); or, 3) The weekly self-monitoring text message assessment only (AO; n = 93). Methamphetamine use at nine months post-enrollment was lower than at baseline in all three arms. The addition of Peer Health Educators and/or theory-based text messages did not produce cost-effective reductions in methamphetamine use over the weekly AO text messages. However, both intervention arms outperformed the AO arm in reducing HIV risk behaviors, but the TXT-Auto arm dominated the TXT-PHE arm in achieving greater reductions in days of methamphetamine use and CAI at lower cost. The TXT-Auto arm achieved greater reductions in CAI than the attentional control at a cost in the base case of ~$37.50 per episode of CAI reduced per month. Sensitivity analyses showed that results were robust to a number of changes in assumptions. Interventions seeking to reduce methamphetamine use among non-treatment-seeking MSM may seek to add minimal attentional control-style text messages to their routines querying about recent methamphetamine use and/or high-risk sex. Interventions seeking to additionally reduce HIV sexual risk behaviors among non-treatment-seeking MSM, specifically engagement in CAI, may seek to additionally apply theory-based text messages.