We penetrate the black box of post-acquisition integration process by examining whether business unit leaders (BULs) —executives responsible for integrating and operating acquired targets— shape integration outcomes. Using text-based and financial measures, we find that BUL target industry experience increases (decreases) integration success (failures) through superior realization of revenue and cost synergies. Other BUL attributes are unrelated to integration outcomes. Consistent with the importance of integration for acquisition success, BUL target industry experience enhances acquisition performance, with effects most pronounced when integration challenges are greatest. BULs add no value at earlier transaction stages, except through integration planning and more extensive due diligence.