Background: The aim was to pilot an adapted manualised weight management programme for persons with mild-moderate intellectual disabilities affected by overweight or obesity ("Shape Up-LD"). Method: Adults with intellectual disabilities were enrolled in a 6-month trial (3-month active intervention and 3-month follow-up) and were individually randomised to "Shape Up-LD" or a usual care control. Feasibility outcomes included recruitment, retention, initial effectiveness and cost. Results: Fifty people were enrolled. Follow-up rates were 78% at 3 months and 74% at 6 months. At 3 and 6 months, controlling for baseline weight, no difference was observed between groups (3 months: [beta]: -0.34, 95% confidence interval [CI]: -2.38, 1.69, 6 months: [beta]: -0.55, 95%CI -4.34, 3.24). Conclusion: It may be possible to carry out a trial of "Shape Up-LD," although barriers to recruitment, carer engagement and questionnaire completion need to be addressed, alongside refinements to the intervention.