This research investigates the role that four organizational and six information system factors, managed by leadership teams, play in predicting the success of post-merger information systems (IS) integration between two companies. Data were gathered using a self-administered, mail and online survey instrument from senior IS executives at firms that have experienced a U.S. public merger greater than $25 million between 2004 and 2007. The results support the research hypotheses that quality of merger planning, quality of communication of merger activities to IS, quality of IS integration planning, degree of end-user involvement in IS integration activities, and quality of technical support to users during the IS integration each have a significant influence on post-merger IS integration success. In addition, based on a supplemental path model analysis, four additional hypotheses are indirectly supported. Although constrained by some limitations, this research contributes to the body of knowledge that identifies sources of IS integration performance, thus further explaining sources of overall merger performance.