Research has found an association between depression, telomere length, and poor health. Interestingly, research has found children of mothers with depression might also have shorter telomeres. A mother’s depression increases a child’s risk for depression through heritability and environmental factors, which has deleterious effects for child health. Further, the 5-HTT genotype could moderate the effects of maternal depression on child some socioemotional outcomes, but the moderating effect of maternal depression on child telomere length and depression has not been tested. This study tested the moderating effect of 5-HTT genotype and child sex for the effect of maternal depression on child and adolescent depression through child telomere length. From a subset (N=2,884) of the large and diverse Fragile Families and Child Wellbeing dataset, we found no support for the mediation or moderation hypotheses. Additional research is needed to better understand the mechanisms through which maternal depression affects child depressive outcomes.