Children of parents with major depressive disorder (MDD) are four to six times more likely than other children to develop MDD. Little research has examined whether comorbid parental diagnoses further increase children's risk. This study examines whether children of parents with comorbid MDD and Borderline Personality Disorder (BPD) (1) are at greater risk for experiencing depressive symptoms and/or episodes and (2) whether such increased risk may be due, in part, to their exhibiting higher levels of cognitive/interpersonal vulnerability factors. Children (n = 140; ages 6-14) of parents with MDD completed measures assessing cognitive/interpersonal vulnerability factors. Parents completed semi-structured clinical interviews assessing severity of current depressive symptoms and BPD. Both children and parents completed a semi-structured clinical interview assessing the child's current and past history of MDD. Children of parents with comorbid MDD and BPD exhibited higher levels of current depressive symptoms and higher levels of cognitive/interpersonal vulnerability factors than children of parents with MDD but no BPD, even after controlling for parents' current levels of depressive symptoms. The relationship between parental BPD and chil-dren's current levels of depressive symptoms was partially mediated by children's cognitive/interpersonal vulnerability factors. Last, children of parents with comorbid BPD and MDD were 6.84 times more likely to exhibit a current or past diagnosis of MDD.