The incorporation of team context into research and practice regarding team effectiveness in NGOs projects is a constant challenge. The research seeks to address the gap and identify the critical determinants of team effectiveness in projects undertaken by non-governmental organizations. Using a systematic process, the study involved both literature and focus group discussions to generate the required items. A total of 157 respondents (Team Members and Team Leaders) were part of the study that filled the questionnaires. Using exploratory factor analysis followed by confirmatory factor analysis, both convergent and discriminant validity was established. The present study found that team effectiveness in NGO social projects has a total of seven dimensions namely: Inter team coordination, community social linkage, team performance, knowledge, skills, and attitudes, leadership communication and engagement, decision making and information sharing, and team formation. There is a significant lack of research on team effectiveness in NGO projects. Where considerably large proportion of research on team effectiveness has focused on the corporate sector, the non-governmental teams have been neglected. This study clearly highlights the determinants that make up team effectiveness in NGOs. The determinants identified will help to specifically look at the effectiveness of teams in NGO projects. The study would help NGOs identify the dimensions in which they may be performing in a weaker manner and direct their energies in improving the factors.