To investigate the association between pelvic floor muscle strength and erectile function in a prospectively collected observational cohort. 270 male volunteers were prospectively collected and grouped by International Index of Erectile Function-5 (IIEF-5) scores. Pelvic floor muscle strength was compared. Patients with obvious neurologic deficits, abnormal pelvic bones, history of pelvic radiation therapy, prostatectomy, or urinary incontinence were excluded. We analyzed 247 patients with mean (± standard deviation, SD) age of 62.8 (± 10.1) years. Mean (± SD) maximal and average strength were 2.0 (± 1.5) and 1.1 (± 0.8) kgf, respectively. Mean (± SD) endurance and IIEF-5 scores were 7.2 (± 2.6) seconds and 13.3 (± 7.9), respectively. Patients with IIEF-5 scores ≤ 12 tended to be older, with a higher occurrence of hypertension and lower body mass index. Age [odds ratio (OR) 1.08, 95% confidence interval (CI) 1.04–1.12, p < 0.001], and maximal strength < 1.9 kgf (OR 2.62, 95% CI 1.38–4.97, p = 0.003) were independent predictors for IIEF-5 scores ≤ 12 in multivariate regression analysis. Patients with erectile dysfunction were older and showed lower pelvic floor muscle maximal strength. Future prospective trials needed for using physiotherapy are required to verify our results.