The Costume Department is responsible for the design, fitting, hire, purchase, manufacture, continuity and care of all costume items on feature films. The term 'Costume' refers to the clothes that the Actors wear, and these differ enormously from production to production, ranging from contemporary urban fashion to period ball-gowns, and even wetsuits. The Costume Department is also responsible for jewellery, footwear, corsetry, hosiery, millinery and sometimes wig-work. Costume is integral in defining the overall 'look' of the film. It provides the audience with information about the period, culture and society the Actors inhabit and, on a more subtle level, the underlying themes of the film itself.

Work in the Costume Department is divided between two 'wardrobes': the 'Making Wardrobe', which incorporates the design, acquisition and creation of costume during pre-production; and the 'Running Wardrobe', which takes care of the organisation, maintenance and continuity of costumes during the film shoot.

The Costume Designer is the Head of the Department, and works closely with the Production Designer and Director to ensure that costumes blend into the overall production design. The Costume Designer oversees a team that usually includes a Costume Design Assistant, Costume Supervisor, Costume Assistants and Costume Dailies. On larger productions, the Costume Designer may employ a team of skilled technicians in a Costume Workshop, which could include cutters, makers, finishers, dyers and milliners. There may also be a Wardrobe Supervisor to oversee the Running Wardrobe.

Job responsibilities for personnel in the Costume Department vary enormously from production to production, depending on the requirements of the Costume Designer. As a result, the boundaries between job roles are blurred, particularly in the case of Costume Design Assistants, Costume Supervisors and Wardrobe Supervisors. During the shoot Costume personnel ensure that costumes are available when required, assist performers with dressing, oversee costume continuity, and maintain and service costumes when not in use. After the shoot Costume personnel ensure that costumes are safely stored, packed and returned to the relevant sources, or sold.