A header connector assembly includes an outer housing, an inner housing, a shield subassembly, and a seal body. The outer housing is disposed in an opening of a panel and includes a cavity. The inner housing includes a channel and is disposed in the opening of the panel. The inner housing is received in the cavity of the outer housing and includes a channel configured to have a contact disposed therein. The shield subassembly is disposed between the outer housing and the inner housing. The shield subassembly engages the panel to electrically couple the shield subassembly with the panel. The seal body is disposed between the panel and at least one of the outer housing and the inner housing. The seal body restricts passage of contaminants between the panel and at least one of the outer housing and the inner housing.