The use of inspection for the governance of human service organisations has increased. However, this type of organisations are hard to control since the tasks they have to perform are often complex and the results are hard to predict. This can be expected to have negative implications for the legitimacy and impact of inspection. The aim of this study is to contribute to an increased knowledge and understanding as to what legitimacy inspection has in social service organisations. In this case study the legitimacy of and adaption to the inspectorate’s demands in two types of inspected social service organisations are investigated: organisations where individuals’ needs for and rights to personal social services are investigated, assessed and decided (IAD), and organisations where treatment interventions are provided (TI). Altogether, 24 politicians, managers and social workers are interviewed. The study shows that the propriety of the inspectors’ descriptions and judgements about the inspected service are questioned less in the IAD than the TI-organisations. Despite this, the results suggest that the social workers in the IAD-organisations are less involved in the development and implementation of the action plans intended to come to terms with the deficiencies identified than do their colleagues in the TI-organisations. The social workers and managers in the IAD-organisations also have less faith in the plans to solve the causes of the deficiencies identified and their mode of adaption is more ritualistic. Abbreviation PSS: Personal social services, IAD: Investigation, assesment and decision making, TI: Treatment interventions, SSA: Social Services Act, NBHW: the National Board of Health and Welfare. © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.