INTRODUCTION: Voltage-gated potassium channels (Kv) are selective transmembrane proteins that allow transport of K+ across the plasma membrane, where they play an important role in establishing the resting potential. They are involved in a variety of biological processes crucial for proper functioning of the cells. In this study we are focused on zebrafish Kcnb1 (Kv2.1), a member of the electrically active Kv2 subfamily of voltage-gated potassium channels. Previously, it has been shown that this protein is expressed in mammalian, Xenopus laevis, and zebrafish inner ear. Based on this, Kv2.1 could be important for development of this organ, where it may be required for proper hearing and spatial orientation. These functions include activity of the mechanosensory cells, which develop a long kinocilium used to export Ca2+ required to form and tether the “hearing stones” – the otoliths (in fish) or otoconia (in mammals). AIM(S): The aim of this study is to investigate the role of Kcnb1 during ear development using zebrafish as a model. METHOD(S): We used morphometric and behavioral analyses to study development of the ear and check hearing and spatial orientation in Kcnb1 mutants and morphants. Using qRT‑PCR we checked level of expression of ear marker genes. Immunohistochemistry was used to stain cilia of the hair cells. RESULTS: Ears of developing zebrafish kcnb1‑/‑ are affected resulting in abnormal morphology and function. Mutants show a significant reduction in size of ears and otoliths as compared to wild‑types. We found changes in the morphology of the hair cells in the ear of kcnb1‑/‑ with changes in orientation of kinocilia. Upregulation and downregulation of some of ear marker genes has been confirmed. Behavioral tests showed defects in hearing and balance in kcnb1‑/‑ and knockdowns. CONCLUSIONS: Our results support a hypothesis that Kcnb1 is important during development and function of the zebrafish ear.