WBP2 encodes the WW domain‐binding protein 2 that acts as a transcriptional coactivator for estrogen receptor α (ESR1) and progesterone receptor (PGR). We reported that the loss of Wbp2 expression leads to progressive high‐frequency hearing loss in mouse, as well as in two deaf children, each carrying two different variants in the WBP2 gene. The earliest abnormality we detect in Wbp2‐deficient mice is a primary defect at inner hair cell afferent synapses. This study defines a new gene involved in the molecular pathway linking hearing impairment to hormonal signalling and provides new therapeutic targets. Synopsis WBP2 was found to underlie deafness in mouse and patients. Wbp2‐deficient mice were used as a genetic tool to gain insight into the functional link between hormonal signalling and hearing impairment. WBP2 mutations lead to deafness in mouse and humans. In the Wbp2‐mutant mouse, the earliest abnormality is swelling of afferent nerve endings below inner hair cells and mice show progressive high‐frequency hearing loss. Wbp2 deficiency leads to reduced expression of estrogen and progesterone receptors in the cochlea and disrupted expression of key post‐synaptic proteins. WBP2 was found to underlie deafness in mouse and patients. Wbp2‐deficient mice were used as a genetic tool to gain insight into the functional link between hormonal signalling and hearing impairment.