Muscle dysmorphia (MD) is a psychological disorder defined by a pathological belief that one lacks muscularity and has excess body fat. To date, treatment research on MD has been sparse. We conducted a pilot feasibility and acceptability study investigating the preliminary efficacy of an 8-week telehealth cognitive-behavioural therapy (CBT) intervention for adults with diagnosed MD. We recruited 10 adults living in Australia who completed eight weekly individual telehealth sessions of a pilot CBT program. We administered a battery of questionnaires assessing MD symptoms, compulsive exercise, and disordered eating at pre-treatment, post-treatment, and three-month follow-up. The program showed promising feasibility and acceptability with no drop-outs from the treatment program once commenced and full completion of all questionnaires at all time points. We observed significant, large reductions in MD symptoms (mean Hedges' g = 1.66), compulsive exercise (g = 1.15), and disordered eating (g = 1.28) from pre- to post-treatment. All treatment improvements were maintained at three-month follow-up. Results provide preliminary support for the feasibility, acceptability and efficacy an 8-week CBT program delivered via telehealth to reduce MD symptoms, compulsive exercise, and disordered eating in adults with MD. These findings need to be tested in controlled trials with larger samples. TRIAL REGISTRATION: This pilot trial was pre-registered on the Australian New Zealand Clinical Trials Registry: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id= 384290&isReview=true.