There is general agreement that acquisition integration is decisive for acquisition performance. Despite this consensus, there are heterogeneous results on integration measures, such as integration speed with empirical research supporting the benefits of either fast or slow integration. We argue that the business environment surrounding acquisitions has the potential to reconcile conflicting findings. We develop how institutional factors (i.e., labor market flexibility and efficiency) influence the relationships between speed of human and functional integration on acquisition performance. With a sample of 203 transactions from acquirers from central Europe and Scandinavia, we find human and functional integration speed have divergent effects on acquisition performance. Further, both relationships are moderated by labor market flexibility and efficiency, but in different ways. Implications for research and practice are discussed.