The anti-müllerian hormone (Amh) pathway is crucial for sexual development in teleosts. A male-specific duplicate of anti-müllerian hormone (amhby) was previously identified as the northern pike (Esox lucius) master sex determination gene. However, the role of its putative cognate receptor, i.e., the anti-müllerian hormone receptor type 2 (amhrII) was unclear in this species. Here, we investigated the role of amhrII during sexual development of northern pike. We generated stable mutants with deletions in exon 9 of amhrII, inactivating the AmhrII protein using a CRISPR-Cas9-mediated gene knockout strategy. The inactivation of amhrII in northern pike results in a high level of male-to-female sex reversal. This result demonstrates that amhrII is necessary for male sexual development in northern pike and supports the idea that AmhrII is a conserved regulator of the teleosts sex differentiation network.