ABSTRACTBackground and AimsCocaine use disorder (CUD) is a significant public health concern for which no efficacious pharmacological interventions are available. Cannabidiol (CBD) has attracted considerable interest as a promising treatment for addiction. This study tested CBD efficacy for reducing craving and preventing relapse in people with CUD.DesignSingle‐site double‐blind randomized controlled superiority trial comparing CBD with placebo.Setting and ParticipantsCentre Hospitalier de l'Université de Montréal, Canada. Seventy‐eight adults (14 women) with moderate to severe CUD participated.InterventionParticipants were randomly assigned (1 : 1) by stratified blocks to daily 800 mg CBD (n = 40) or placebo (n = 38). They first underwent an inpatient detoxification phase lasting 10 days. Those who completed this phase entered a 12‐week outpatient follow‐up.MeasurementsPrimary outcomes were drug–cue‐induced craving during detoxication and time‐to‐cocaine relapse during subsequent outpatient treatment.FindingsDuring drug–cue exposure, craving scores [mean ± standard deviation (SD)] increased from baseline by 4.69 (2.89) versus 3.21 (2.78) points, respectively, in CBD (n = 36) and placebo (n = 28) participants [confidence interval (CI) = −0.33 to 3.04; P = 0.069; Bayes factor = 0.498]. All but three participants relapsed to cocaine by week 12 with similar risk for CBD (n = 34) and placebo (n = 27) participants (hazard ratio = 1.20, CI = 0.65–2.20, P = 0.51; Bayes factor = 0.152). CBD treatment was well tolerated and associated mainly with diarrhoea.ConclusionsCBD did not reduce cocaine craving or relapse among people being treated for CUD.