The Modified Caregiver Strain Index is a widely used tool to screen for caregiver strain in family caregivers. This study presents the Portuguese version of the Modified Caregiver Strain Index and explores its psychometric properties in a sample of 347 informal caregivers of older dependent individuals. Factor analysis revealed a two-factor structure and indicated satisfactory internal consistency. Criterion-related validity was supported by positive significant correlations with the emotional health of the caregiver (psychological distress).