Addison's disease, also known as primary adrenal insufficiency (PAI), is a rare endocrine disorder characterized by a decrease in all three adrenal hormones. This case report describes a 32-year-old female who presented with generalized weakness, fatigue, weight loss, and hyperpigmentation. Based on her symptoms and laboratory findings, a diagnosis of Addison's disease was made. She was started on hormone replacement therapy, and her symptoms improved significantly.