The present study aimed to validate the Italian 8-item, 9-item, and 12-item versions of the Depression, Anxiety and Stress Scale-21 (DASS-21), addressing the need for shorter yet psychometrically robust measures. Two studies were conducted with different samples. In Study 1 (n = 541), confirmatory factor analysis (CFA) and reliability testing of the short-form versions of the DASS were performed, and their convergent validity with life satisfaction and mental well-being was examined. Study 2 (n = 321) extended this validation by reassessing factor structure, reliability, and convergent validity using constructs associated with psychological distress, including positive and negative affect, self-esteem, and perceived stress. Results demonstrated that all short-form versions retained the three-factor structure of the original DASS-21, with overall sufficient fit indices, especially the 9-item model. Reliability metrics confirmed internal consistency (all Cronbach’s alpha and McDonald’s omega ≥0.70). Convergent validity analyses indicated strong correlations between the short-form versions of DASS-21 (min = 0.675, max = 0.956) and associated psychological constructs, aligning with theoretical expectations. The scales captured the relationships between psychological distress, positive and negative affect, perceived stress, mental well-being, self-esteem, and life satisfaction. Findings suggest that the Italian versions of the DASS-8, DASS-9, and DASS-12 provide feasible and reliable alternatives to the DASS-21 for assessing depression, anxiety, and stress, supporting their usefulness in clinical and research contexts, particularly in circumstances in which brevity is essential.