There is little evidence on the costs associated with the route of administration of oncology drugs. We investigated time and resource use for hospitals and patients and compared healthcare and societal costs for intravenous (IV) and subcutaneous (SC) administration of trastuzumab and rituximab. Data for the preparation and administration of both drugs were collected at the hospital pharmacy and at the oncology day care unit. Patients completed a questionnaire for obtaining information on societal costs (productivity losses, informal care and traveling expenses). A total of 126 patients were recruited in six hospitals; 82 received trastuzumab (37 IV and 45 SC) and 44 received rituximab (23 IV and 21 SC). The costs per administration (including societal cost but excluding drug costs) were €167 and €264 for IV and €76 and €146 for SC trastuzumab and rituximab, respectively. The costs for SC administration were lower in all categories. The largest cost component was related to time spent at the day care unit (overhead costs). This resulted in savings of €47 for SC trastuzumab and €69 for SC rituximab. The costs related to time of healthcare professionals was €9 lower for both drugs. The costs for consumables resulted in another €12 savings. Societal costs were €22 lower for SC trastuzumab and €28 lower for SC rituximab. Although administration costs are relatively a small part of the total costs, important savings can be generated by switching to an SC route of administration especially because a large number of patients receive oncology drugs and patients receive more than one administration.