This study investigated potential differences in mental health among children living in sole physical custody (SPC), asymmetric joint physical custody (JPC), and symmetric JPC; and it tested whether children’s age moderated the association between physical custody arrangements and children’s mental health. Using data from the Family Models in Germany (FAMOD) and Norwegian Dynamics of Family Conflict (FAMC) studies, we estimated OLS regression models for children aged 2 to 14. In the German sample, children in asymmetric JPC had fewer mental health problems than children in SPC. However, this difference disappeared when controlling for various background variables, including the quality of parent-child relationships. Additionally, children’s age moderated the association between physical custody arrangements and children’s mental health problems, with increasing age being related to fewer mental health problems in asymmetric JPC. This association remained even after controlling for the background variables. In the Norwegian sample, no differences were found in children’s mental health across physical custody arrangements; nor did children’s age moderate the association. The results of this study emphasize that there may be cultural differences in how children’s mental health is related to their physical custody arrangements. Furthermore, there are modest indications that asymmetric JPC may be related to better mental health among older children in Germany.