Despite the growth of data-rich environments and the increase in data accessibility, studies have offered limited insights into how to lead and control information technology (IT) outsourcing projects to benefit from these trends. To address the research gap, this study investigates the effect of big data accessibility on project performance, and analyzes the moderating effects of vendors’ leadership styles and outsourcers’ control mechanisms from a vendor's perspective. Based on absorptive capacity theory, we develop five hypotheses and examine them using data from 195 IT outsourcing projects. The results show that big data accessibility has a positive effect on IT outsourcing project performance, but that the effect varies with vendors’ leadership styles and outsourcers’ control mechanisms. Specifically, the positive effect of big data accessibility is weakened by vendors’ transactional leadership and outsourcers’ behavior-based control, whereas it is strengthened by vendors’ transformational leadership and outsourcers’ outcome-based control. This study contributes to the literature by identifying distinct roles of different leadership styles and different control mechanisms in leveraging big data accessibility.