Objective: To evaluate tamsulosin (α-blocker therapy) for male overactive bladder (OAB) and to examine if indicators of concomitant benign prostatic hyperplasia are associated with OAB symptom improvement. Materials and Methods: This was a planned, exploratory analysis of a 4-week, α-blocker (tamsulosin 0.4 mg) run-in phase of the Male Overactive Bladder Trial in Veterans (MOTIVE). Participants with urinary urgency and urinary frequency (> 8 voids/24 hours) completed bladder diaries, answered symptom questionnaires (AUA-7 SI), and had post-void residual and noninvasive uroflowmetry measurement. Results: A total of 116 male Veterans aged 42-88 years with OAB participated. There were statistically significant reductions in voiding frequency (11.3 > 10.0 voids/24 hours, P < .0001), urgency scores (mean 2.5-2.2 points, P < .0001), and nightly nocturia (2.1 > 1.8, P < .001). Only baseline AUA-7 SI total and voiding subscale categories (mild, moderate, severe) were associated with significant reduction in AUA-7 SI total score. For continuous variables, only AUA-7 SI baseline total score was associated with AUA-7 SI storage symptom changes. No other baseline measures were associated with changes in urgency, frequency, or nocturia. Conclusion: Initiation of short course tamsulosin therapy in men was associated with statistical reduction in OAB symptoms. Baseline post-void residual, uroflow rate, and the voiding symptom subscore of the AUA-7 SI were not predictive of OAB symptom improvement with tamsulosin. These findings merits further exploration.