Purpose Over the last decade, penile low-intensity extracorporeal shockwave therapy (LI-ESWT) has emerged as a promising alternative for the treatment of erectile dysfunction (ED). The aim of this trial is to assess the effect of electromagnetic LI-ESWT on the erectile function of vascular phosphodiesterase type 5 inhibitor (PDE5I) refractory ED patients. Methods Randomized, double-blind, sham-controlled study. 76 patients with vascular PDE5I-refractory ED completed the study. 40 men were treated with LI-ESWT (1 session/week for 4 weeks, 5000 shocks/session, 0.09 mJ/mm(2)energy density) and 36 were treated with a sham probe. Baseline and post-treatment (1, 3 and 6 months) evaluations were performed using validated erectile function questionnaires (IIEF-EF, EHS, SEP2, SEP3 and GAQ1). The groups were compared using Mann-Whitney-Wilcoxon and chi-squared tests, with results considered statistically significant atp < 0.05. Results At the 3-month follow-up, median change in IIEF-EF score for active and sham groups was 3.5 (IQR 0-10) and - 0.5 (IQR - 11 to 1), respectively (p < 0.05). Six months after treatment, 52.5% of patients (21/40) in the active group and 27.8% of patients (10/36) in the sham group presented an EHS > 2 (p < 0.05). At the same evaluation, 40.0% (16/40) and 13.9% (5/36) of patients had positive answers to GAQ-1, in the treated and sham groups, respectively (p < 0.05). No adverse events were observed during the study. Conclusion This study showed that penile electromagnetic shockwave therapy may improve erectile function, to a modest extent, on certain patients that do not respond to PDE5I; making it an alternative for vascular ED patients that reject more invasive therapies.