Either parent may file a petition to modify a child custody order—but usually only when there is a substantial change in circumstances that affects the child (including changes in one or both of the parents’ lives) that justifies the court revisiting and possibly modifying the earlier child custody order.

The petition to modify child custody generally must be filed in the same court in which the parents’ divorce case was decided. But if the child lives in a different county or state, the courts of the county or state where the child lives may be the proper place to file a petition to modify a child custody order.

In Arizona, either parent has the right to file a petition to modify a child custody order. However, the court typically requires that there be a substantial change in circumstances that affects the welfare of the child before it will reconsider the existing order. This change could be related to either parent's life or other factors that impact the child's best interests. When filing a petition to modify child custody, it is generally required to do so in the same court where the original divorce and custody decisions were made. If the child has since moved to a different county or state, the petition may need to be filed in the jurisdiction where the child currently resides. The court will then determine if it has jurisdiction to hear the case, considering factors such as the child's home state and the length of time the child has resided there. It's important for parents to understand that the primary concern of the court is the best interests of the child, and any modifications to custody orders will be evaluated with this in mind.