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). The findings show evidence of reliability and validity of the Portuguese version of the Modified Caregiver Strain Index encouraging its use in clinical and research fields.