Mitcham Girls High School students belong to one of three houses, which form the basis for competition in athletics, swimming and other events. Each house has a team of Captains, one from each year level, who have been elected by their peers. These House Captains take a leadership role as they manage their house teams during Sports Day, Swimming Carnival and lunchtime House Sports competitions. At the end of the year the house with the most points is presented with the Collyer Cup. The three Houses are:
Named after Dame Roma Mitchell; red represents the legal colour worn by judges.
Named after Dawn Fraser the Olympic swimmer; representing the water.
Named after author Catherine Helen Spence; represents the colour of writing paper often used in the early 1900s.