Background: The prevalence of urological diseases increases with age, and lower urinary tract symptoms (LUTSs) are the most common problem. Natural compounds with minimal side effects for the improvement in LUTSs are of ongoing interest. Salvia miltiorrhiza root extract (SAGX) has shown potential in preclinical studies for its effects on LUTSs. Objectives: This multicenter, randomized, double-blind, placebo-controlled study aimed to evaluate the efficacy and safety of SAGX in men with lower urinary tract symptoms (LUTSs) over a 12-week period. Methods: A total of 136 subjects were randomized to receive either 400 mg or 800 mg of SAGX or a placebo daily, orally. The primary outcome was the change in the International Prostate Symptom Score (IPSS). Secondary outcomes included changes in prostate-specific antigen (PSA), testosterone levels, urinary flow rate, residual urine volume, and erectile function as measured by the International Index of Erectile Function (IIEF). Results: Both SAGX intake groups showed statistically significant improvements in total IPSS scores and several secondary outcomes compared with the placebo group. Notable improvements were observed in symptoms of incomplete emptying, frequency, intermittency, weak stream, urgency, nocturia, and quality of life scores. Erectile function, as assessed by the IIEF, also significantly improved, especially in the 400 mg SAGX intake group. No significant differences were found in PSA levels or testosterone levels. No serious adverse events leading to discontinuation of the study drug were observed in the SAGX groups. Conclusions: With fewer side effects than conventional treatments, SAGX is effective and safe in improving symptoms of lower urinary tract symptoms and enhancing erectile function in men.