Objectives This study determines the effects of comorbidity of mood disorder and alcohol use disorder on suicide behavior. Methods We converted data from the electronic medical records of one university hospital into a common data model and utilized it in our analysis. We selected 9551 patients with diagnosis codes of mood disorders or alcohol use disorders and divided them into three groups: mood disorder (MD) only, alcohol use disorder (AUD) only, and comorbidity of mood disorder and alcohol use disorder (MD+AUD). The mood disorder group was also subgrouped with depressive (DD) or bipolar affective disorder (BD) groups, and the comorbidity group was classified in the same way. Then, we applied logistic regression analysis to assess the risk of suicide attempts between the diagnostic groups. Subgroup analysis according to age also was conducted. Results The MD+AUD group had 2.7 (odd ratio [OR]=2.70, 95% confidence intervals [CI]=1.91- 3.81, p<0.0001) and the DD+AUD group had 2.78 (OR=2.78, 95% CI=1.95-3.98, p<0.0001) times higher risk of suicide attempts than the MD only and DD only group, respectively. Furthermore, according to the age subgroup, the risk of suicide attempts was the highest (OR=5.17, 95% CI=2.35-11.40, p<0.0001) in the DD+AUD group for those aged 40-59. There were no significant results in BD. Conclusion The results showed that the comorbidity of mood disorder and alcohol use disorder could increase suicide risk. This study suggested that alcohol use behavior needs to be assessed as well as mood symptoms for suicide prevention.