This review explores the association between GJB2 gene mutations, encoding connexin 26 (Cx26), and nonsyndromic hearing loss. Connexins are proteins that form intracellular membrane channels and regulate ion movement between contiguous fluid spaces. A family of autosomal gene mutations has been identified that lead to abnormal connexin expression within the inner ear that are associated with hearing loss. The exact mechanism by which this link is elicited remains unclear. We aim to highlight the clinically underestimated prevalence of GJB2 gene mutations, to explore the influential role of ethnic diversity in mutation frequency, and to provide a framework for hearing specialists in considering the differential diagnosis of nonsyndromic hearing loss. By linking an observed phenotype associated with abnormal Cx26 expression to the current understanding of the biological and genetic basis underlying it will allow a more accurate clinical description of associated hearing loss, and therefore enable more effective patient management and genetic counselling.