PurposeThe purpose of this paper is to try to identify the critical success factors and problems in ISO 9000 maintenance during the post‐certification period. Much of the published work on issues associated with ISO 9000 certification in the quality management journals focuses on how to obtain certification and the impact of certification on ISO‐certified organisations. Thus, studies do not generally address what happens after the organisations have obtained their certification.Design/methodology/approachIn total, 14 face‐to‐face interviews were conducted over a period of seven weeks with top management, middle management, lower management in charge of operations and quality, and the management representative responsible for the implementation of ISO 9000 in the case study organisation (XYZ). Each interview lasted between 1.5 and 2 hours. ISO documents were also reviewed as part of the data gathering process.FindingsThe results showed that people who comprise top management, other employees, the reward system, teamwork, continuous improvement, understanding of ISO itself, measurement of performance and communication are all critical success factors for ISO 9000 maintenance of XYZ. Apart from continuous improvement, other factors also seemed to be consistent with the findings from other studies. In contrast to the other studies, the current study found continuous improvement of process, people, and system as several of the critical success factors for the sustainable quality management system at XYZ.Originality/valueThis paper makes a contribution to the body of knowledge in the field of quality management systems during the post‐certification period where such work is limited, especially in the service sector.