Objective: Adherence to prescribed medications is crucial to prevention and control of cardiovascular diseases among people at risk for metabolic syndrome including diabetes. However, there is a lack of evidence concerning psycho-behavioral interventions to improve medication adherence among this population. To systematically review the evidence of available published studies that evaluated psycho-behavioral interventions to improve medication adherence. Methods: The participants were currently using prescribed medication or initiated medication therapy. Methodological quality of each study was assessed with Effective Public Health Practice Project Quality Assessment Tool for Quantitative Studies. The Comprehensive Meta-Analysis software package ver2.0 was used to calculate the effect size as an odds ratio (OR) with a 95% confidence interval(CI). Heterogeneity was analyzed with Q statistics and the I2 index. Results: Noticeable research trends in psycho-behavioral interventions were found: specifically, intervention targets are being broadened from patients to healthcare providers; community-based and population-based interventions are increasing; and intervention strategies are being diversified and combined. Most of the studies used multiple strategies with a mode of 3 intervention strategies used out of 15 categories and ranging from 1 to 7. ‘Education’ was the most frequently used strategy, followed by ‘monitoring’, ‘training’, ‘problem-solving’, ‘counselling’, ‘behavioral reinforcement’, ‘process modification’, and ‘social support’ etc. The pooled effect size using the random effects model on medication adherence was statistically significant (I2 = 63.5%; P < 0.001; OR 1.507, 95% CI 1.244-1.827). Conclusion: Multifaceted interventions with psycho-behavioral strategies were used to improve medication adherence in people at risk for metabolic syndrome in the selected studies. However, the level of abstractness of reported strategies varied. Further research is required to clearly categorize diverse psycho-behavioral strategies on the basis of taxonomic criteria. * This research was support by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (grant number: 2013R1A1A2059806).