Although maternal stress during pregnancy and even before conception shapes offspring risk for mental health problems, relatively little is known about the mechanisms through which these associations operate. In theory, preconception and prenatal stress may affect offspring mental health by influencing child responses to postnatal caregiving. To address this knowledge gap, this study had two aims. First, we examined associations between preconception and prenatal stress with child temperament profiles at age four using multilevel assessment of maternal perceived stress and stress physiology. Second, we tested child temperament profiles as moderators of associations between observed parenting behaviors during a parent-child free-play interaction when children were 4 years old and child behavior problems 1 year later. Latent profile analyses yielded four distinct child temperament profiles: inhibited, exuberant, regulated low reactive, and regulated high reactive. Consistent with hypotheses, preconception, and prenatal stress each independently predicted the likelihood of children having temperament profiles characterized by higher negative emotionality and lower regulation. Specifically, preconception perceived stress and prenatal cortisol predicted likelihood of children having an exuberant temperament, whereas prenatal perceived stress predicted likelihood of children having an inhibited temperament. Contrary to hypotheses, temperament profiles did not moderate predictions of child behavior problems from observed parenting behaviors; however, responsive parenting behaviors inversely predicted child behavior problems independently of child temperament. These findings add to growing evidence regarding effects of preconception factors on child outcomes and underscore a central role for responsive parenting behaviors in predicting more favorable child mental health independent of child temperament. (PsycInfo Database Record (c) 2024 APA, all rights reserved).