To modify an existing child custody order in Texas, one must file a modification case. If the child’s interests are no longer being served by the child custody arrangement, or if circumstances have changed, a modification may be granted.   The fastest way to obtain a modified child custody order is to reach an agreement on the matter and submit that agreement to the court. However, if the parties cannot agree on the terms of a new custody arrangement, the court must decide them on behalf of the parties. Common reasons for requesting a modification include: Job relocation Health conditions Either parent is suspected of abusing or neglecting the children Marital status changes A parent has a substance abuse problem or criminal proceedings Unemployment