This study utilized a sequential mixed method approach in developing a model for team effectiveness in Philippine organizations. In the first phase, qualitative data were gathered to elicit the factors that were deemed important to creating effective teams. In the second phase, a survey composed of three factors identified in the first phase: team member competencies, quality of relations, and leadership, was administered to 418 employees from 85 Filipino work teams from various sectors and industries. Results revealed that the three significant predictors accounted for 60% of the variance in perceived team effectiveness. The proposed model of input-process-output was partially supported. Results showed that quality of relations partially mediated the relationship of leadership and team member competence on perceived team effectiveness. The study highlights the importance of social relations especially in the Philippine context and underscores the value of understanding team effectiveness from a cultural perspective.