Background: Neurodegenerative diseases (NDs) are one of the main causes of disability and dependence that have a great impact both on the quality of life of people with disabilities and their families. A majority of people with NDs receive care and support from the family, but there is no tool in Spain with which to measure whole-family QOL. The aim of this study was the translation, cultural adaptation, and validation of the FQOLS-Dementia into Spanish to assess FQOL among family members of individuals with NDs who live in the Spain-Portugal cross-border area.