Background <p>Ultra-processed food (UPF) consumption is increasing rapidly across Southeast Asia, yet its potential psychological effects remain insufficiently explored. This review synthesized regional evidence on the association between UPF intake and psychological distress and related psychosocial outcomes.</p> Methods <p>A systematic search of nine international and regional databases (2011–2025) identified studies assessing NOVA Group 4 UPFs with UPF intake and psychological distress and related psychosocial outcomes. Two reviewers independently screened studies, extracted data, and assessed methodological quality using the ROBINS-E tool. Findings were integrated through thematic analysis.</p> Results <p>Seven cross-sectional studies from Malaysia and Thailand, and a multi-country Southeast Asian adolescent cohort, met the inclusion criteria. Higher consumption of UPFs such as sugar-sweetened beverages, energy drinks, fast foods, and sweets, was associated with greater depressive, anxiety, and stress symptoms as the primary psychological distress outcomes. Other related psychosocial outcomes included poorer sleep quality, heightened behaviors related to Attention-Deficit/Hyperactivity Disorder (ADHD), reduced cognitive performance, and increased loneliness and suicidality. However, existing limitations such as reliance on self-reported measures, small convenience samples, and non-standardized UPF assessments restricted the generalizability of results.</p> Conclusion <p>Findings suggest that UPF consumption may be an emerging behavioral risk factor for psychological distress and related psychosocial outcomes in selected countries in Southeast Asia, aligning with concepts on Nutritional Psychiatry. However, causal inference is limited by the nature of the included studies. To further understand this association and to guide effective public health action, longitudinal studies using standardized and culturally appropriate measures are needed.</p>