This thesis has explored multifaceted nature of depression through the lens of cognitive theory and therapy. From examining the foundation principle of Beck’s cognitive triad and the role of schema and the cognitive distortions to evaluating the efficacy of CBT an its various adaptation, this work has highlighted the significant contribution of cognitive approaches to understanding and treating the disorder. Cognitive theory provides the robust framework for understanding depression, and CBT offers a valuable and adaptable therapeutic approach. As the cognitive approaches continuously refined and new approach innovated, the future strives toward more accessible, more effective, and more personalized treatments to alleviated global burden of depression and empower individual to achieve long-lasting results and well-being.