•Compared to placebo, adjuvant ginseng improved sexual functions.•Both female and male individuals reported improvements in sexual functions.•Ginseng appears to be a valuable add-on to treat methadone-induced sexual dysfunction. While methadone maintenance therapy (MMT) in patients with opioid use disorder (OUD) decreases the risk of substance use relapses and criminal and risky sexual behavior, a major disadvantage is its negative impact on sexual function. In the present study we tested whether, compared to placebo, ginseng extract ameliorates methadone-related sexual dysfunction among female and male patients with OUD and receiving MMT. A total of 74 patients (26 females: mean age: M = 39.0 years; 48 males; mean age: 40.64 years) took part in a double-blind, randomized and placebo-controlled study. Female and male patients were separately randomly assigned either to the ginseng or to a placebo condition. At the beginning of the study and four weeks later, patients completed questionnaires on sexual function. Irrespective of gender, sexual function improved over time, but more so in the ginseng condition than in the placebo condition. Ginseng appears to counteract the sexual dysfunction resulting from methadone use in both female and male patients with OUD and undergoing MMT.