The current study sought to clarify the role of phosphodiesterase type 5 inhibitors (PDE-5i) and a vacuum erection device (VED) in penile rehabilitation after laparoscopic nerve-preserving radical proctectomy (LNRP) for rectal cancer. Participants were assigned to one of the following arms—no-intervention, nightly use of sildenafil 25 mg for 3 months after surgery, or concurrent use of nightly sildenafil 25 mg/day for 3 months and a vacuum erection device (VED) 10 to 15 minutes/day for 3 months—in a nonrandomized fashion. All participants had a follow-up of over 12 months prospectively, and patients had baseline, 3-, 6-, and 12-month assessment based on the International Index of Erectile Function–5 (IIEF-5). Seventy-one cases were included in final analyses. In the no-intervention group, the mean baseline IIEF-5 score of 21.9 decreased rapidly to 5.0 at 3 months (p < .001), 9.2 at 6 months (p < .001), and stayed at 10.9 at 12 months (p < .001). In the single therapy group, the mean baseline IIEF-5 score of 22.4 decreased dramatically to 9.0 at 3 months (p < .001), 14.9 at 6 months (p = .005), and stayed at 15.1 at 12 months (p = .005). In the combined therapy group, the mean baseline IIEF-5 score of 23.0 decreased slightly to 15.0 at 3 months (p = .005), 18.0 at 6 months (p = .038), and maintained at 18.7 at 12 months (p = .163). Findings suggested an over 50% decline in the quality of erection function of the patients after LNRP. The early use of PDE-5i alone or combined use of PDE-5i and VED after LNRP maintained erectile function at 12 months.