OBJECTIVES: There is a paucity of data on postoperative exercise and how it relates to surgical failure, specifically after midurethral sling (MUS) surgery. We aimed to assess if women with higher self-reported activity levels as measured by strenuous exercise are more likely to experience stress urinary incontinence (SUI) symptoms after MUS than women with lower self-reported activity. METHODS: This is a secondary analysis of Operations and Pelvic Muscle Training in the Management of Apical Support Loss: the OPTIMAL Trial, a randomized trial comparing sacrospinous ligament suspension versus uterosacral ligament suspension, both with concomitant retropubic MUS. Participants completed a validated assessment of activity preoperatively and postoperatively. Women in the upper quartile for strenuous exercise (≥90 minutes per week) were compared with the remaining participants. Symptomatic SUI was defined as retreatment or reoperation for SUI and/or any positive response to Pelvic Floor Disorders Inventory stress incontinence questions 20 to 22. RESULTS: A total of 351 participants in the OPTIMAL study received MUS along with their prolapse repair and had postoperative exercise and Pelvic Floor Disorders Inventory data. At 2 years, 87 (29%) of 305 exercised strenuously for at least 90 minutes per week, and 63 (23%) of 277 experienced SUI. Women who were less active at 2 years were significantly more likely to experience SUI than women who were more active (26.6% vs 12.8%, P = 0.0138). CONCLUSIONS: In this study, symptomatic SUI occurred more frequently in women with lower self-reported exercise levels 2 years after MUS surgery.