Background: Elevated morning cortisol is a prospective predictor of major depression and may serve as a vulnerability marker. We examined the relation between morning cortisol and two prominent risk factors for depression in preschool-aged children: maternal depression and child temperament. We also explored whether maternal depression during the child's life, parental hostility and life stress explained these associations. Methods: Ninety-four children provided a morning salivary cortisol sample, and 92 children provided an evening sample. Child temperament and parenting were assessed using observational measures, and maternal depression and life stress were assessed with clinical interviews. Results: Maternal history of melancholic depression and child temperamental low positive emotionality were significantly associated with higher morning cortisol. These relations persisted after controlling for children's negative emotionality and concurrent depressive symptoms, parental hostility, and life stress. Conclusions: Our findings support the hypothesis that elevated morning cortisol may serve as an early-emerging vulnerability factor for depression, and highlight the importance of anhedonia in risk for depression.