Abstract: A vehicle interior illumination lamp mounting structure includes a roof panel and a bracket. The roof panel is formed with an opening. A first connector is to be mounted on a ceiling. The bracket includes a bracket hook portion to be locked on an edge of the opening. A second connector, to be fitted to the first connector mounted on the ceiling by rotating the bracket, is locked on the bracket. The first connector includes a first wall and a second wall which are configured to receive the second connector therebetween. The first wall is situated far away from the bracket hook portion than the second wall in a state where the bracket is locked on the opening. A length of the first wall is longer than a length of the second wall in a rotating direction of the bracket.