The forests of the East Usambara Mountains, Tanzania, are internationally recognized as one of the worlds’ most bio-diverse ecosystems. Despite past conservation efforts, these forests face an on-going threat from land clearing for smallholder agriculture and timber harvesting. As many remaining fragments of forest lie on farmers’ properties, often in the form of modified agroforestry systems, a potential means to slow or halt forest loss is a ‘payments for ecosystem services’ (PES) programme, where farmers are paid to protect trees on their farms. For such a programme to achieve its goals, careful consideration of farmers’ preferences for PES is required. Using a choice experiment, this study quantifies these preferences, and in addition, determines the approximate payment amount required to attract farmer support. Notable results are that payment for manure fertilizer (representing an investment in farm productivity) was highly effective at motivating farmer support, a group payment was highly ineffective, and that minimal programme conditionality was not always preferred. Required payment amounts were found to be highly variable between farmers. The paper concludes with a discussion of PES programme design practicalities as informed by the study findings.