Objective: This study is a randomized trial of a Web-based intervention to increase condom use among college women. Participants: From October 2012 to March 2013, N = 422 completed baseline questionnaires and intervention procedures. n = 216 completed 3-month follow-up. Methods: Participants completed a decisional balance exercise examining their sex acts over the past 3 months and wrote an essay encouraging young girls to use condoms. All procedures were conducted online. Results: The intervention improved intentions to use and attitudes towards condoms for 3 subscales of condom attitudes. Attitudes following the intervention significantly predicted condom use at 3-month follow-up, and this relationship was mediated by condom intentions immediately post intervention. The relationship between intentions and condom use was moderated by group. Conclusions: The intervention improved condom attitudes and intentions immediately post intervention, and immediately post intervention intentions had a greater impact on condom use at 3-month follow-up among those in the condom intervention compared with those in the control group.