Study Objectives: To compare the efficacy of guided online and individual face-to-face cognitive behavioral treatment for insomnia (CBT-I) to a wait-list condition. Methods: A randomized controlled trial comparing three conditions: guided online; face-to-face; wait-list. Posttest measurements were administered to all conditions, along with 3-and 6-mo follow-up assessments to the online and face-to-face conditions. Ninety media-recruited participants meeting the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for insomnia were randomly allocated to either guided online CBT-I (n = 30), individual face-to-face CBT-I (n = 30), or wait-list (n = 30). Results: At post-assessment, the online (Cohen d = 1.2) and face-to-face (Cohen d = 2.3) intervention groups showed significantly larger treatment effects than the wait-list group on insomnia severity (insomnia severity index). Large treatment effects were also found for the sleep diary estimates (except for total sleep time), and anxiety and depression measures (for depression only in the face-to-face condition). Face-to-face treatment yielded a statistically larger treatment effect (Cohen d = 0.9) on insomnia severity than the online condition at all time points. In addition, a moderate differential effect size favoring face-to-face treatment emerged at the 3-and 6-mo follow-up on all sleep diary estimates. Face-to-face treatment further outperformed online treatment on depression and anxiety outcomes. Conclusions: These data show superior performance of face-to-face treatment relative to online treatment. Yet, our results also suggest that online treatment may offer a potentially cost-effective alternative to and complement face-to-face treatment.