Background <p>The Patient Health Questionnaire-9 (PHQ-9) is one of the most widely used instruments worldwide for screening and quantifying the severity of depressive symptoms. Its brevity, public-domain availability, and strong empirical support have facilitated its broad adoption across clinical and research settings. However, despite its extensive international use, evidence regarding its psychometric performance in the Dominican Republic remains limited. The absence of locally validated instruments entails critical challenges, including reduced diagnostic accuracy, suboptimal assessment of symptom severity, and constraints on clinical decision-making and context-sensitive mental health research. Establishing the validity and reliability of the PHQ-9 in this context is therefore essential to support both applied screening efforts and epidemiological investigations. The present study examined the internal structure, reliability, and convergent validity evidence of the PHQ-9 in a Dominican adult sample.</p> Methods <p>A total of 914 adults participated in the study. Dimensionality was evaluated using parallel analysis based on polychoric correlations and exploratory factor analysis with principal axis factoring. Construct validity evidence was further examined through confirmatory factor analysis using the diagonally weighted least squares estimator. Internal consistency was assessed using McDonald’s omega and Cronbach’s alpha coefficients. Convergent validity evidence was estimated through Spearman correlations between PHQ-9 and Generalized Anxiety Disorder-7 (GAD-7) scores.</p> Results <p>Findings supported a robust unidimensional structure. Although parallel analysis based on polychoric correlations suggested more than one factor, inspection of the eigenvalue structure, principal axis factor loadings, and confirmatory factor analysis supported retention of a one-factor solution. Reliability indices indicated high internal consistency, with both omega and alpha coefficients exceeding .80. PHQ-9 scores showed strong positive associations with GAD-7 scores, providing convergent validity evidence consistent with the well-documented overlap between depressive and anxiety symptomatology.</p> Conclusions <p>The PHQ-9 demonstrates solid psychometric performance in Dominican adults, supporting its use as a reliable screening measure of depressive symptom severity in both research and applied settings. These findings extend cross-cultural validation evidence to a previously underexamined Caribbean context. Future studies incorporating structured clinical interviews and depression-specific gold-standard measures are warranted to further examine diagnostic validity, measurement invariance, and optimal cut-off scores.</p>