While the past four decades have seen unprecedented increases in rates of both childhood obesity and parental incarceration, it remains unknown whether parental incarceration is associated with an increased risk of unhealthy weight among young children. We address this question using a sample of nine-year-olds from the Fragile Families and Child Wellbeing Study, testing for effects separately by whether the mother, father, or both parents have a history of incarceration. Diverging from findings linking paternal incarceration to negative child behavioral outcomes, here we find no effect of incarcerated fathers on child body mass, while maternal incarceration is associated with significantly lower odds of overweight. Findings are consistent with an emerging body of research suggesting that the effects of maternal incarceration may differ from those of paternal incarceration, and caution against generalizing the direction of behavioral and mental health effects of parental incarceration to child physical health conditions.