Context: Estimates of the prevalence of chemsex among men who have sex with men (MSM) range from 3% to 29%. There are several health risks associated with chemsex such as higher exposure to STIs, depression, anxiety, cognitive impairments and social consequences. Very few validated psychotherapeutic interventions have been designed or tested for this population, even though chemsex is a public health issue. Objective: To examine the feasibility, acceptability and preliminary efficacy results of a specific 8-session group cognitive and behavioral therapy (CBT) intervention for MSM seeking treatment for problematic chemsex practice. Method: We included 38 participants in a weekly group CBT program that combined psychoeducation, harm reduction, and exercises on topics related to addiction and sexuality. Participants were assessed at the inclusion, 4 and 8 weeks, on the frequency of chemsex practice (TimeLine Follow back), substance use disorder (Drug Use Disorder Identification Test) and craving (Craving Experience Questionnaire). Results: Acceptability was 95%, median attendance was 6 out of 8 sessions [IQR=4-7] and 19% of participants attended all sessions. Significant decreases were observed between baseline and week 8 in the DUDIT (p = 0.005; r = 0.63) and CEQ scores (frequency: p=0.025; r=0.5; intensity: p=0.019; r=0.55). Perspectives: There is evidence of good feasibility and promising results for this intervention. Assessment of quality of life and further evaluation of sexual behavior should be included in future research. Controlled, randomized trials should be designed to state on the efficacy of this program.