OBJECTIVES:To estimate total direct costs of psychiatric hospital diary and its components of costs in a public psychiatric hospital the Complexo Hospitalar Juquery.METHODS: A retrospective cost study covering six months period (from July to December, 2015) and using top down approach, from public health provider´s perspective was designed to estimate the mean direct cost per patient per day in a psychiatric unit with 128 subjects. Components of costs were: capital costs (equipment and furniture), hotel costs (support services, transport, overhead, consumables, and human resources) and treatment costs (medication).RESULTS:: The mean direct costs per patient per day was BRL373,79. Clinical human resources accounted for 48,75%, hotel costs for 30,44%, , overhead costs for 11,41%, Non-clinical human resources costs for 7,24%, consumables and clothes costs for 0,99%, medicamentos costs for 0,69%, and capital costs for 0,47%.CONCLUSIONS:: National public reimbursement for one psychiatric hospital diary correspond to 10% of total direct costs of diary per patient. Then, the majority of hospital costs was funded by the State Governement and and not by the Federal Governement. Resource allocation for planning deinstitutionalization implies in taking into account these hospital costs to be transferred to the community services according to these patient’s needs and also to evaluate how these resources are allocated in terms of regional and local level.