Background: Weight loss is important for the control of type 2 diabetes mellitus but is difficult to achieve and sustain. Programmes employing financial incentives have been successful in areas such as smoking cessation. However, the optimum design for an incentivised programme for weight loss is undetermined, and may depend on social, cultural and demographic factors. Methods: An original questionnaire was designed whose items addressed respondent personal and health characteristics, and preferences for a hypothetical incentivised weight loss programme. One hundred people with type 2 diabetes mellitus were recruited to complete the questionnaire from the endocrinology clinic of a public hospital in Lima, Peru. A descriptive analysis of responses was performed. Results: Ninety-five percent of subjects who had previously attempted to lose weight had found this either 'difficult' or 'very difficult'. Eighty-five percent of subjects would participate in an incentivised weight loss programme. Median suggested incentive for 1 kg weight loss every 2 weeks over 9 months was PEN 100 (~USD $30). Cash was preferred by 70% as payment method. Only 56% of subjects would participate in a deposit-contract scheme, and the median suggested deposit amount was PEN 20 (~USD $6). Eighty percent of subjects would share the incentive with a helper, and family members were the most common choice of helper. Conclusions: The challenge of achieving and sustaining weight loss is confirmed in this setting. Direct cash payments of PEN 100 were generally preferred, with substantial scope for involving a co-participant with whom the incentive could be shared. Employing direct financial incentives in future weight loss programmes appears to be widely acceptable among people with type 2 diabetes mellitus.