Significance The inner ear is a vertebrate organ of delicate and complex architecture that translates sound into electrical signals deciphered by the brain. This study utilizes a genetic approach to associate a mutation of ROR1 (receptor tyrosine kinase-like orphan receptor 1) with inner ear anomalies and deafness in humans. Characterization of Ror1 mutant mice reveals fasciculation deficiencies of spiral ganglion axons and disruption of sensory hair cell synapses and peripheral innervations. The molecular basis of this phenotype involves alterations of the NF-κB pathway. Thus, we present ROR1 as a previously unrecognized gene that is essential for the development of the inner ear and hearing in humans and mice.