Purpose: The aim of this study was to identify factors influencing on the mental health in bereaved adults. Methods: A descriptive and correlational study was conducted in 160 adults who had experienced bereavement. The collected data was analyzed using descriptive statistics, Pearson’s correlation, and hierarchical multiple linear regression analyses with SPSS 26.0. Results: The participants’ mental health showed a positive correlation with complicated grief (r=.31, p<.001) and a negative correlation with grief and meaning reconstruction (r=-.30, p<.001). Sex, sleeping time, intimacy with the deceased, grief reaction, and grief and meaning reconstruction were significant factors influencing on the mental health. The total explanatory power of these variables was 31.8%. Conclusion: It is necessary to explore the persistent and impairing grief after experiencing bereavement. Our study findings will be fundamental evidence to develop nursing interventions to improve adult mental health dealing with bereavement and grief.