Personality and social support (SS) influence risk for depression and modify its outcome through multiple pathways. The impact of personality dimensions neuroticism and extraversion on SS among patients with major depressive disorder (MDD) has been little studied. In the Vantaa Depression Study, we assessed neuroticism and extraversion with the Eysenck Personality Inventory, objective SS with the Interview Measure of Social Relationships, and subjective SS with the Perceived Social Support Scale-Revised at baseline, at 6 and 18 months among 193 major depressive disorder patients diagnosed according to the fourth edition of Diagnostic and Statistical Manual of Mental Disorders (DMS-IV). At all time-points, low neuroticism and high extraversion associated significantly with between-subject differences in levels of objective and subjective SS. Lower neuroticism (beta = 0.213, p = 0.003) and higher extraversion (beta = 0. 159, p = 0.038) predicted greater within-subject change of subjective, but not objective SS. Thus, neuroticism and extraversion associated with the size of objective and subjective SS and predicted change of subjective SS. Modification of subjective SS, particularly, may indirectly influence future vulnerability to depression.