Objectives Liraglutide is a glucagon-like-peptide-1 receptor agonist which has been used as an anti-obesity drug. It was reported that patients might develop or worsen suicidal ideas and/or depression during liraglutide treatment, especially when it comes to patients with a psychiatric disorder. The purpose of this study was to evaluate the effectiveness and safety of liraglutide, especially in terms of the psychiatric adverse effects. Methods A retrospective chart review study was conducted on psychiatric patients prescribed liraglutide for more than one month from September 2018 to September 2020. Based on their medical records, we investigated the change in the weight and body mass index (BMI) of patients from the baseline to 6 months of receiving liraglutide treatment. Information on the adverse effects was also obtained, including psychiatric adverse effects such as insomnia, anxiety, depression, and suicidal ideation. A mixed linear model was used for assessing the time effect on change in weight and BMI. Results A total of 24 patients were included in the current study, and the most common psychiatric diagnosis included major depressive disorder (n=13, 54.2%). There was a significant change in weight (F=6.127, p=0.001) and BMI (F=6.749, p<0.001) during the liraglutide treatment. Worsening of depression and anxiety occurred in one patient but improved after the adjustment of psychiatric medications. Conclusion The current study found that liraglutide treatment in patients with a psychiatric disorder can be a safe and effective intervention for weight reduction.