Forests and water are important Common Pool Resources (CPRs) in the Uluguru Mountains (UMs). Water connects socio-economic groups of different altitudinal zonation namely upstream and downstream with multiple uses and conflicting interests. Researches have been done on ecosystem value, CPRs depletions and the role of socio- economic incentives in biodiversity conservation but little is known about power relations underlying upstream and downstream CPRs users. This study therefore, was conducted with the objective of assessing power relations between upstream and downstream CPR users and mapping winners and losers under prevailing management regimes. The study was carried out in four villages, two in upstream (Ruvuma and Peko Misegese) and the other two in the downstream (Mafisa and Mlali). Qualitative and quantitative data were collected. Qualitative data were analyzed by means of content analysis technique. Descriptive and inferential statistical analyses were employed to analyze quantitative data. Social Network Analysis was used to analyse interactions of stakeholders. Forty four stakeholders were identified that are involved in the management and utilization of forest and water. The identified stakeholders fall into three categories namely regulators, facilitators and users. The study further identified three types of power: strategic, institutional and structural embedded in peoples’ livelihood in both upstream and downstream. Strategic power was found to be dominant in the upstream while institutional power was dominant in the downstream. The study revealed conflictive power relation which created winners and losers, whereby upstream dwellers were the winners. Also the study revealed the existence of resource use conflicts that centred on power relations between upstream and downstream. Furthermore, the study identified existing formal and informal conflict resolution mechanisms. The study concludes that resource use conflicts in the Uluguru Mountains are consequence of poweriii imbalance between upstream and downstream communities. The study recommends the need of forming stakeholders’ platforms and improving institutional arrangements.