Although the detrimental effects of poverty on child mental health are well established, questions remain as to which aspects of poverty matter most and which mechanisms account for the association. This study tested the relative influence of depth of current poverty and poverty duration on child anxiety/depression and antisocial behavior, then evaluated whether parenting practices mediated observed associations. Data come from four waves of the Canadian National Longitudinal Survey of Children and Youth (1994–2000), with analysis restricted to children who were aged 2 to 5 at initial interview and lived with both biological parents throughout (n = 1,901). Depth of current poverty was associated with child anxiety/depression, whereas persistent poverty was associated with child antisocial behavior. Parenting behaviors were significant predictors but did not mediate the association between poverty dynamics and child mental health. The research and policy implications of these findings are discussed.