BackgroundVaping cessation is virtually unexplored. The efficacy and safety of varenicline for vaping cessation has not been studied and rigorous research is required to advance best practice and outcomes for people who use electronic cigarettes (EC) and want to quit. The objective is to evaluate the efficacy and safety of varenicline (1 mg BID, administered for 12 weeks, with follow-up to week 24) combined with vaping cessation counseling in exclusive daily EC users intending to quit vaping.MethodsDesign: Double-blind, randomized, parallel-group, placebo-controlled trial.Setting: The study took place at a University-run smoking cessation center.Participants: People who exclusively use ECs daily and intend to quit vaping.Intervention: A total of 140 subjects were randomized to either varenicline (1 mg, administered twice daily for 12 weeks) plus counseling or placebo treatment (administered twice daily, for 12 weeks) plus counseling. The trial consisted of a 12-week treatment phase followed by a 12-week follow-up, nontreatment phase.Main outcomes and measures: The primary efficacy endpoint of the study was biochemically validated continuous abstinence rate (CAR) at weeks 4 to 12. Secondary efficacy end points were CAR at weeks 4 to 24 and 7-day point prevalence of vaping abstinence at weeks 12 and 24.ResultsCAR was significantly higher for varenicline vs placebo at each interval: weeks 4–12, 40.0% and 20.0%, respectively (OR = 2.67, 95% CI = [1.25–5.68],P= 0.011); weeks 4–24, 34.3% for varenicline with counseling and 17.2% for placebo with counseling (OR = 2.52, 95% CI = [1.14–5.58],P= 0.0224). The 7-day point prevalence of vaping abstinence was also higher for the varenicline than placebo at each time point. Serious adverse events were infrequent in both groups and not treatment-related.ConclusionsThe findings of the present RCT indicate that inclusion of varenicline in a vaping cessation program for people who use electronic cigarettes and intending to quit may result in prolonged abstinence. These positive findings establish a benchmark of intervention effectiveness, may support the use of varenicline combined with counseling in vaping cessation programs, and may also help guiding future recommendations by health authorities and healthcare providers.Trial registrationThe study has been registered in EUDRACT with Trial registration ID: 2016-000339-42.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12916-023-02919-2.