This study sought to explore the existing indigenous knowledge system (IKS) in four villages bordering the South Nguru Mountain Forest Reserve; to find out its significance in the conservation of biodiversity and to examine factors that influenced the system's integration into biodiversity conservation methods in the area. Using the exploratory cross-sectional research approach, and guided by the political ecology theoiy, this study triangulated interviews, focus group discussions (FGDs) and field observation to collect data from 240 randomly selected indigenous people; 60 from each study village. The Statistical Package for Social Sciences (SPSS) and content analysis were used to analyse quantitative and qualitative data respectively. This study revealed that IKS was embedded in the indigenous social structure and local politics, cultural norms, values and spiritual beliefs, with selective conservation. Social, demographic and economic factors were also seen to overtly influence integration of IKS into conservation methods, so was the lack of official recognition and capacity building of the indigenous social structures. In conclusion, despite Tanzania being a signatory of the 1992 Rio De Jeneiro Convention on Biological Diversity (CBD) and the Tanzania Forest Act of 2002 on active participation of indigenous people in biodiversity conservation, IKS and biodiversity conservation methods operate in a parallel and win-lose, rather than a win-win relationship. Recommendations put forth focus on official recognition of the IKS and active participation of the actors; motivation and capacity building; training on the significance of the IKS and addressing the problem of household-level poverty, while considering the demographic and socio-economic contexts of the local population.