ACK1, a widely expressed non-receptor tyrosine kinase, is often amplified in cancer and has been shown to interact with Cdc42, EGFR and several other cancer relevant molecules, suggesting a possible role for ACK1 in development and tumor formation. To directly address this scenario, we generated mice lacking a functional ACK1 gene (ACK1 ko) using CRISPR genome editing. ACK1 ko mice developed normally, displayed no obvious defect in tissue maintenance and were fertile. Primary ACK1-null keratinocytes showed normal phosphorylation of EGFR, but a tendency towards reduced activation of Akt and Erk. DMBA/TPA induced skin tumor formation did not reveal significant differences between ACK1 ko and control mice. Deletion of the ACK1 gene in the breast cancer cells lines MDA-MB-231, 67NR, MCF7, 4T1 and T47D caused no differences in growth. Furthermore, EGF-induced phosphorylation kinetics of Erk, Akt and p130Cas were not detectably altered in T47D cells by the loss of ACK1. Finally, loss of ACK1 in MDA-MB-231 and T47D breast cancer cells had a very limited or no effect on directed cell migration. These data do not support a major role for ACK1 in Cdc42 and EGFR signaling, development, or in tumor formation.