Mutations in known melanoma predisposition genes CDKN2A, CDK4, BAP1, and the TERT promoter account for approximately half of familial melanoma cases. We exome sequenced 184 individuals from 105 cutaneous melanoma families from Australia, the UK and the Netherlands to search for novel melanoma susceptibility genes that might account for the remaining risk. We found co-segregating mutations in the protection of telomeres 1 (POT1) gene in two families (a 5-case family from Australia and a 3-case family from the UK) and also in three singleton cases. Mutation carriers generally presented with early onset disease and multiple primary melanomas. We found that missense mutations in the oligonucleotide-/oligosaccharide-binding (OB) domains of POT1 disrupted its binding to telomeric repeat DNA. As telomere dysregulation plays an important role in tumorigenesis, these findings, in combination with the recently described familial melanoma TERT promoter mutation, significantly extend our understanding of a novel pathway predisposing to the development of melanoma. This information may be used to better manage this disease in mutation carriers and ultimately may lead to the development of novel therapies to treat melanoma.