The decision to have bariatric surgery should be based on accurate information on possible risks and benefits of all treatment options. The goal of this study was to determine whether a video-based bariatric decision aid intervention results in superior decision quality compared to an educational booklet. We conducted a prospective, randomized controlled trial among adult patients in a single health plan who met standard criteria for bariatric surgery. Patients were randomly assigned to review either a video-based decision aid (intervention) or an educational booklet on bariatric surgery (control). Changes in patient decision quality were assessed using bariatric-specific measures of knowledge, values, and treatment preference after 3 months. Of 152 eligible participants, 75 were randomly assigned to the intervention and 77 to the control. The 3-month follow-up rate was 95%. Among all participants, significant improvements were observed in knowledge (P < 0.001), values concordance (P = 0.009), decisional conflict (P < 0.001), decisional self-efficacy (P < 0.001), and in the proportion who were "unsure" of their treatment choice (P < 0.001). The intervention group had larger improvements in knowledge (P = 0.03), decisional conflict (P = 0.03), and outcome expectancies (P = 0.001). The proportion of participants choosing bariatric surgery did not differ significantly between groups, although there was a trend toward decreased surgical choice in the intervention group (59% booklet vs. 42% video at 3 months; P = 0.16). The use of bariatric surgery decision aids was followed by improved decision quality and reduced uncertainty about treatment at 3 months. The video-based decision aid appeared to have a greater impact than the educational booklet on patient knowledge, decisional conflict, and outcome expectancies.