Abstract Background The rise in student depression and anxiety highlights a crucial intersection between education and public health. Academic pressures intensify mental health issues, necessitating comprehensive strategies to address them. Objectives This study assessed the effectiveness of a Psychological Capital (PsyCap) intervention in enhancing university students’ PsyCap and reducing anxiety, aligning with broader public health education goals. Methods A randomized controlled trial was conducted, where students either received a PsyCap intervention or were placed on a wait-list. The intervention, based on Luthans et al.’s guidelines, was delivered online and included self-reflection, goal-setting, and resource assessment. Results Post-intervention, the PsyCap of students in the intervention group significantly increased (M = 1.098, SD = 0.24, CI [0.98, 1.21], t(17) = 19.72, p < .001). There was also a significant reduction in GAD scores (M = -0.24, SD = 0.46, CI [-0.47, -0.01], t(17) = -2.19, p = .043). No significant changes were observed in the control group. Conclusions Short-term PsyCap interventions can significantly improve students’ mental resilience and decrease anxiety, suggesting their integration into educational curricula. This study underlines the need for educational and public health sectors to collaborate in mitigating mental health issues among students, particularly in response to crises like COVID-19. Addressing the rising anxiety among students through brief, online PsyCap interventions shows promise. This approach not only enhances PsyCap but also lowers anxiety, advocating for their regular inclusion in educational settings to support student mental health. Key messages • Results from a controlled trial revealed increases in PsyCap and decreases in anxiety.Findings advocate integrating such interventions into educational curricula promoting student mental health. • Recent trends indicate a rise in anxiety among students, challenging both educational and public health. Addressing this, the study evaluated the impact of a brief online (PsyCap) intervention.