Objectives: This study aimed to investigate the effect of trospium chloride on cognitive function in postmenopausal women treated for overactive bladder (OAB). Methods: Randomized double-blind placebo-controlled trial conducted from April 2013 to April 2015. Women aged 50 years or older seeking treatment for OAB were randomized to either trospium chloride XR 60 mg daily or placebo. Baseline cognitive function was assessed via Hopkins Verbal Learning Test-Revised (HVLT-R), Mini Mental Status Exam, Mini Mental Status X, Digit Span, Trails A, Trails B, and Epworth Sleepiness Scale. Cognitive function was reassessed at week 1 and week 4. A priori power analysis determined that 21 subjects were needed per group. Results: Although 59 women were enrolled and randomized (28 trospium and 31 placebo), 45 completed assessment (21 trospium and 24 placebo). Mean age was 68 years, 78% were white, and 44% had previously taken OAB medication. For the primary outcome, there was no difference in HVLT-R total score between trospium and placebo groups at week 4 (P = 0.29). There were also no differences based on the other cognitive tests. Therewas a correlation between age and the following week-4 tests: HVLT-R total score (r = -0.3, P = 0.02), HVLT-R total recall subscale (r = -0.4, P = 0.007), Trails A (r = 0.4, P = 0.002), and Trails B (r = 0.4, P = 0.004). A linear regression model found that HVLT-R total score decreased by 0.372 points for each increased year of age. Conclusions: In women aged 50 years and older, there were no changes in cognitive function between those taking trospium and placebo. Cognitive function was correlated with age.