Context ISD research based on the socio-technical perspective suggests that two sources of socio-technical change have a bearing on the performance of information systems development (ISD) projects: business requirements and development technology. To enhance project effectiveness, ISD teams need to enhance their flexibility in the face of the constant changes taking place from business and technical environments in which they operate. Flexibility is conceptualized as an outcome of capability development through constantly integrating and reconfiguring available resources within and outside of the organization where the team is embedded. Objective The purpose of this study is to examine the relationship between a team’s external social capital and team flexibility. More specifically, based on social capital theory, this study argues that external social capital leads to IS team flexibility, which in turn contributes to the successful project performance. Method A survey design was selected to collect data and test the proposed model. A snowballing strategy was employed to collect data. 118 information systems developers participated in the survey and the model was analyzed using partial least squares regression. Results: The findings show that, in general, the ISD teams’ external social capital do contribute to the team’s response to changes. However, they exhibit unique impacts on ISD team flexibility respectively. Results The findings show that, in general, the ISD teams’ external social capital does contribute to the team’s response to changes. However, they exhibit unique impacts on ISD team flexibility respectively. Conclusion The various external social capitals have distinctive effects on a team’s flexibility. Specifically, horizontal relationships are positively associated with both business and technology flexibility. Vertical relationships are positively associated with business flexibility and market relationships technology flexibility. ISD managers should establish robust relationships with its high-ups, other lateral units, and third parties outside in the market. They also need to be more adaptive to the increasingly volatile socio-technical environment, and proactively search, exploit, upgrade, and integrate resources that are essential to the development of system development team flexibility.