The Office is required by the Inspector of Custodial Services Act (2003) to inspect each prison, detention centre, court custody centre and prescribed lock up in Western Australia at least once every three years. The Inspector has autonomous authority to decide which facilities to inspect and in what order. However, the Act (2003) provides that the responsible Minister may direct the Inspector to conduct an inspection or review of a custodial service.

Inspections may be announced, unannounced, full inspections or light-touch inspections as decided by the Inspector.

Most inspections are announced. The Office maintains unannounced inspections should not be over-utilised. To do so may diminish the potency of this approach. In any case, as the Office follows a philosophy of 'continuous inspection' by means of regular liaison visits to each prison and other custodial centre or service, the necessity for unannounced inspections is reduced.