Introduction: The current study examined the psychometric properties of the Portuguese version of the Family Distress Index (FDI). The FDI is an 8-item self-report measure that assesses family maladaptation, providing an index of family outcomes within the resiliency model of family stress, adjustment, and adaptation. Method: Participants were 459 adults, who completed measures of family distress (FDI) and family functioning (Systemic Clinical Outcome Routine Evaluation; SCORE-15). Results: Exploratory and confirmatory factor analyses supported a unidimensional factorial structure. Results also indicated that the FDI has good internal consistency and temporal stability. The positive and significant correlation between FDI and SCORE-15′ scores demonstrated its convergent validity. Through receiver operating characteristic (ROC) analysis, we determined a cut-off score of 12 for identifying probable family distress. Discussion: In sum, the Portuguese version of the FDI is a valid and reliable instrument, which can foster the development of future empirical studies focused on family adaptation in diverse contexts of adversity, namely in health care settings.