Objective: This study aimed to examine the differences in personality, defense style, and coping styles among patients with depression according to age groups. Methods: A total of 211 participants ranging from 19 to 81 years old were recruited for the study. To assess participants’ five dimensions of personality, the Neuroticism-Extraversion-Openness Personality Inventory-Revised (NEO-PI-R) was administered. In addition, the Korean-Defense Style Questionnaire and the Korean version of the coping checklist were administered to examine the defense and coping style. Results: In the analysis of NEO-PI-R, the mean value of Agreeableness, Conscientiousness, and Neuroticism showed significant differences between the young adult age group (20-34 years) and the late middle age group (50-64 years) (p<0.05). The young age group used more immature defense styles and made less use of problem-focused coping strategy than the old age patients (65 years and older) (p<0.05). Conclusion: In the young age group associations with lower Agreeableness and Conscientiousness, as well as higher Neuroticism than the late middle age group were observed. Moreover, the young age group had a higher usage of immature defense style, and restricted use of problem-focused coping style than other age groups.