Fibromyalgia syndrome (FMS) is characterized by chronic widespread pain, fatigue, anxiety, depression, and sleep disturbances, significantly impairing quality of life and psychological well-being. Well-being therapy (WBT) is a brief psychotherapeutic intervention aimed at increasing well-being and optimizing functioning, which has proven effective in treating various conditions involving pain and psychological or psychiatric symptoms. We describe a case study of a 22-year-old university student experiencing FMS, highlighting the far-reaching effects of the condition on her quality of life. After eight sessions of WBT, there was a marked improvement in subjective well-being and euthymia, as well as a decrease in pain perception, improved ability to manage stress, reduced allostatic overload despite the presence of stressors, improved social relationships, and increased self-efficacy. The positive effects of WBT continued at 3-month follow-up, suggesting that WBT may represent a short-term effective intervention for patients with FMS.