Recent research findings have revealed that CSOs play very important hands on role to bring about social and economic change to developing countries like Tanzania. The CSOs are very diverse and unique in terms of set up, mission and mandate, there is therefore no single model on how should CSOs perform their functions in Tanzania. However, there are common held approaches that apply to effective management practices and so bring about good outcomes to the neediest people in Tanzania. This study has evidenced CSOs having a pivotal role to beef up service provision by the government and private sectors to spearhead socioeconomic development by explaining roles CSOs have been having in bringing such developments in Tanzania. This study has confirmed findings from previous studies that number, roles and diversity of CSOs increased significantly from 1980s to 1990s, and consequently involvement of CSOs in service provision has increased dramatically in recent years. Among the CSOs under this study, the ones which have been on board for more than five years have been seen to operate in coordinated multiple fields compared to the CSOs which have been on board for less than five years which operate in fewer fields. This study has evidenced increased annual budgets over time among the studied CSOs in Tanzania and this is an indication that CSOs’ performance capacity to manage projects and finances has improved over time. The current increased performance capacity of CSOs addresses the raised critique regarding managerial competence of CSOs in developing countries like Tanzania. The need for CSOs addressing issues in line with priority areas which are highlighted in the Tanzania’s National Strategy for Growth and Poverty Reduction (NSGRP) for rapid socioeconomic development of Tanzania has come out clearly from the findings of this study. This study recommends a more comprehensive study of CSOs to capture more issues and cover bigger geographical areas than what was done by this study.. This will help identify more areas which need improvement in future to strengthen the CSO sector and benefit ultimate project beneficiaries in Tanzania.