Obesity is a major health issue worldwide. Treating adults with obesity often involves lifestyle and diet changes and sometimes medication. Liraglutide is a drug that is being closely studied for treating obesity. However, the potential side effects of liraglutide, particularly its impact on mood and the development of depression, may be of concern. Given the frequent co-occurrence of obesity and depression, it is important to understand how obesity treatments like liraglutide might affect a person’s mood. A 47-year-old schoolteacher with no personal or family history of mental illness or chronic physical condition sought help for his steadily increasing weight. Despite having a sedentary job and reporting no major stress or substance use, he did not attempt to change his diet or activity level, occasionally experiencing sleep difficulties. He was overweight, with a body mass index of 42. The patient was diagnosed with adult obesity and prescribed liraglutide, diet changes, and exercise. Initially, he lost weight, but he also developed depressive symptoms, including fatigue, loss of interest, sleep disturbances, and suicidal ideation. Following cessation of liraglutide treatment, his depression symptoms got better, but his weight slightly increased. This case sheds light on the possible link between liraglutide and depression in managing obesity. It is crucial for healthcare providers to be aware of potential mental health side effects of obesity drugs like liraglutide. Although the exact reasons behind these mood changes are not fully understood, this case emphasizes the need for careful observation and decision-making in treatment. Understanding these issues can help balance the benefits and risks of liraglutide and ensure better care and treatment options for people with obesity.