Objective: The identification of reliable predictors of course in major depressive disorder (MDD) has been difficult. Evidence suggests that the co-occurrence of personality pathology is associated with longer time to MDD remission. Interpersonal pathoplasticity, the mutually influencing nonetiological relationship between psychopathology and interpersonal traits, offers an avenue for examining specific personality vulnerabilities that may be associated with depressive course. Method: This study examined 312 participants with and without a co-occurring personality disorder diagnosis who met criteria for a current MDD episode at baseline and who were followed for 10 years in the Collaborative Longitudinal Personality Disorders Study. Results: Latent profile analysis (LPA) identified 6 interpersonal groups (extraverted, dominant, arrogant, cold, submissive, and unassuming), and circular statistical profile analysis confirmed group interpersonal distinctiveness. No significant differences between groups were found in comorbid Axis I disorders or baseline MDD severity. Chronicity and functioning analyses found significantly greater chronicity and poorer functioning in individuals with a submissive interpersonal style over 10 years. Conclusions: These findings support the relevance of interpersonal pathoplasticity in depressive course and that this heterogeneity has clinical significance. This study is the first to use LPA and circular profiles to examine interpersonal heterogeneity within a diagnostic group. The implications of these findings for therapeutic intervention, interpersonal functioning, and psychopathological course are discussed. (Contains 7 footnotes, 5 tables, and 3 figures.)