Purpose: This study aimed to examine the effectiveness of non-pharmacological interventions to reduce depressive or anxiety symptoms in undergraduate nursing students. Methods: The electronic databases searched included Embase, CINAHL, PubMed, PsycINFO, Cochrane CENTRAL, ScienceOn, KISS, and KoreaMed to find randomized controlled trials (RCTs) published between 2010 and 2021. A total of 18 RCTs were included in the analysis. The RCTs focused on depression (7 studies), anxiety (14 studies) and both (3 studies). Results: Psychological interventions showed a large, significant effect (Hedges G = -1.20; 95% CI = -2.28, -0.13) and mindfulness interventions showed moderate, significant effects (Hedges G = -0.53; 95% CI = -0.78, -0.27) on decreasing depressive symptoms. Meanwhile, mindfulness interventions showed a large, significant effect (Hedges G = -1.06; 95% CI = -1.98, -0.15) and biofeedback interventions also showed a large, significant effect (Hedges G = -0.99; 95% CI = -1.33, -0.64) on decreasing anxiety symptoms. Conclusion: Non-pharmacological interventions such as psychological, mindfulness, and biofeedback programs could be effective in alleviating depressive and anxiety symptoms in order to improve mental health among nursing students.