Background: Social comparison orientation reflects a relatively stable tendency to evaluate one's abilities, opinions, and social position by referring to other people. Although social comparison has been linked to psychological distress, evidence simultaneously examining depression, anxiety, and stress among Vietnamese young adults remains limited. This study examined the associations and statistical predictive role of social comparison orientation in relation to depression, anxiety, and stress among Vietnamese young adults. A quantitative cross-sectional design was used. Data were collected through an online self-report survey from March to June 2026 using convenience and snowball sampling. The final sample comprised 306 participants. Social comparison orientation was measured with the 11-item Iowa-Netherlands Comparison Orientation Measure, while depression, anxiety, and stress were assessed with the 21-item Depression Anxiety Stress Scales. Pearson correlations and three hierarchical linear regressions were conducted in IBM SPSS Statistics 27. Gender was entered at Step 1 and social comparison orientation at Step 2. Social comparison orientation was positively associated with depression (r = .236), anxiety (r = .228), and stress (r = .265), all p < .001. After gender was controlled, it significantly predicted depression (beta = .243; total R-squared = .063), anxiety (beta = .236; total R-squared = .063), and stress (beta = .267; total R-squared = .081). It explained an additional 5.8%, 5.5%, and 7.1% of the variance, respectively. Gender did not contribute significantly to any final model. A stronger tendency to evaluate the self through comparison with others was consistently associated with higher negative emotional states, with the largest association observed for stress. The findings support prevention and counseling approaches that help young adults recognize maladaptive comparison patterns and develop more self-referenced standards of evaluation. Causal conclusions are not warranted because the data were cross-sectional.