The existing alliance between the two caregivers is a key dimension for understanding the family context, as it affects parental behavior and children’s development. The assessment of this construct becomes even more pressing in at-risk families, where the children’s well-being may be compromised and where the parental alliance may serve as a protective factor. The Parental Alliance Inventory (PAI) is a self-report measure that assesses the parental alliance and the relationship of support and trust that exists between both parents. In this study, we intended to explore the psychometric properties of PAI in the Portuguese population, including normative and at-risk families. Participants were community parents (n = 205, M = 38.38 years; 52.2% women) and parents of Child Welfare Services (CWS) referred children (n = 273, M = 37.05 years, 82.05% women). Both samples completed the PAI and measures of parenting sense of competence, parenting stress, and marital satisfaction. Confirmatory factor analysis confirmed the proposed original unidimensional structure of the PAI. The instrument showed good psychometric properties, presenting levels of internal consistency and a quite satisfactory reliability. Findings also showed that PAI was measurement invariant across the two subsamples. Our findings provide evidence for psychometric soundness of the PAI and support its usefulness for the European Portuguese context.
