The study assesses the influence of the dimensions of agency’s capacities to the performance in generating own sources revenues in the government agencies in Tanzania. The study used institutional theory and contingency theory, an explanatory case study strategy together with survey methods to assess the influence of government agencies’ capacities to the performance in generating own sources' revenues. Data were collected by administering 80 questionnaires to agency’s senior officers who were members of the management team and staff at large. The government agencies that were purposively selected to be part of this study were National Housing and Building Research Agency (NHBRA), Agency for Development of Educational Management (ADEM) and Taasisi ya Sanaa na Utamaduni Bagamoyo (TaSUBa).The findings of this study revealed that planning and development, human resource, and infrastructure capacity significantly and positively influence the performance of the agency in generating own source revenues. However, financial capacity and good governance were found to have insignificant influence. This might be contributed by the fact that there were ineffective governance practices in term of ineffective committees, poor policies and procedures as it was revealed in descriptive analysis. It is concluded that the critical capacities which strongly and positively influence the performance of the agency in generating own source revenues are planning and development capacity, human resource capacity, and infrastructure capacity. The study recommends that these government agencies must find more sources of revenue, consider seriously the issue of motivation to staff, operate competitively, have complex and good long term strategic plans and aim at implementing them. The implication of the study findings is that it contributes knowledge to the administrative actors and also policy and regulation makers such as the parliament of Tanzania, the office of the CAG and ministry for finance to form policies on the five dimensions of capacity that will enable government agencies to improve and grow