The main objective of this study was to assess the opportunity costs of REDD+ to the communities of Mufindi District. The specific objectives were, to identify and assess the economic value of alternative land use, the aboveground carbon stock of the sampled forest (Idewa Forest Reserve) under PFM, the profitability of each land use and compare with the REDD+ incentives, and the willingness to accept (WTA) of the communities towards REDD+. Structured and semi structured questionnaires, personal observation, focused group discussion and forest inventory were used in data collection. Sixty households out of 975 in two villages were sampled randomly. The data was analyzed using the SPSS programme version 16 and Microsoft Excel programme. Descriptive analysis was used to generate frequencies, percentages, Chi square values, sums and means which were used to discuss the results. The main land uses were agriculture and tree planting. Main crops cultivated include maize and beans, and tree species planted was Pinus patula. The economic value for agriculture and tree planting were $ 2 958.52 and $3 272.94 per ha per year respectively. The aboveground carbon of the sampled forest was 39.23 t/ha (143.97 tCO2e/ha). The opportunity costs of REDD+ was varying depending on the price per ton of carbon. The general perception of the communities in the study area towards REDD+/PFM was positive (53.3%) and their willingness to accept was positive. The opportunity costs of REDD+ to the communities will be advantageous if the price per ton of carbon dioxide equivalent will be $23 and above. Therefore there is no general unit price per tCO2e. I therefore recommends opportunity costs of REDD+ to different communities be used as guidance when making decision on unit prices of carbon.Climate Change Impact Adaptation and Mitigation Program (CCIAM)