Continued use of acquisitions despite evidence that they do not improve firm performance suggests that challenges associated with acquisitions may be underestimated by managers. We examine how employee resistance is influenced by acquisition integration and how it results in lower acquisition performance. Specifically, we examine different impacts of task and human integration on employee resistance in a sample of 92 Nordic mid-size firms. Task integration focuses on achieving synergies from increased efficiency; however, it can increase employee resistance, leading to lower acquisition performance, which is exacerbated by slow integration. Meanwhile, human integration can reduce employee resistance, and this effect is stronger for experienced acquirers. Our results support the importance of considering both task and human integration, as their influence on employee resistance varies. Additional implications for management research and practice are identified.