Objective: Theory of mind (ToM) is a foundational ability for social functioning and interpersonal relationships. This study aims to examine theory of mind components in major depressive disorder and its relationship with metacognitive functions and attachment styles. Method: The study enrolled 64 patients with major depressive disorder and 64 healthy controls. The control group was selected to match the patient group regarding age, gender, marital status, and educational level. Every participant completed the sociodemographic data form, the Hinting Test, the Reading the Mind in the Eyes Test, the Adult Attachment Style Scale, and the Metacognition Questionnaire. The severity of depression symptoms was evaluated using Hamilton Depression Rating Scale-17. Results: The average overall score of the metacognition questionnaire was substantially greater in the patient group (p<0.001) compared to the control group. The average score for the Hinting Task was substantially lower in the patients compared to the control group (p<0.001). The severity of depressive symptoms showed a strong negative correlation with the Hinting Task score (r=-0.759; p<0.001), and a moderate negative correlation with the Reading the Mind in the Eyes Test score (r=-0.589; p<0.001). Conclusion: This study showed that depressed individuals have impairments in reading the minds of others’ around them and in their metacognitive functions. The findings above highlight the need to integrate techniques centered on enhancing fundamental theory of mind reasoning into current therapy interventions in order to enhance the comprehension and interpretation of social information among individuals experiencing depression. Keywords: Attachment, Depression, Metacognition, Theory of Mind