Objectives To identify non-invasive predictors of response to tamsulosin 0.4 mg in patients with benign prostatic obstruction (BPO). Methods Males ≥ 50 years of age with lower urinary tract symptoms (LUTS) suggestive of BPO for over three months were included in the study. We assessed change in the mean International Prostate Symptom Score (IPSS) and maximum flow rate (Qmax) after six weeks of medical therapy. Clinical and uroflowmetry parameters were compared between two groups of patients with >25% vs. <25% change in the IPSS after treatment. Pre- and post-treatment post-void residue (PVR), Qmax, and IPSS were compared by independent t-test, univariate/multivariate regression analysis. Results A total of 121 patients were included. At presentation, the mean prostate size was 35.7±12.2 grams and the mean IPSS was 16.3 ± 4.8. Improvement in the mean IPSS was 7.83, with more marked improvement in storage compared to voiding LUTS (5.26 vs. 2.57). Majority (58%) had a quality of life (QoL) score of 4-5 at presentation whereas after 6-weeks of medication (83.5%) had a QoL score of 0-2. Treatment failure was noted in 11 (9.1%) patients. IPSS was higher and Qmax was lower at the time of presentation in patients who had <25% improvement. However, the two groups were identical on the basis of demographic and other factors (BMI, age, prostate size, PVR). Conclusion Moderate LUTS secondary to BPO responds favourably to alpha-blocker (tamsulosin 0.4 mg) treatment. Uroflowmetry (UFM) parameters, that is, Qmax and IPSS are important factors in predicting short-term response to medical therapy.