Background: In 2010, an accreditation system for occupational health services (OHS) in Norway was implemented. Aims: To examine OHS experiences of the accreditation system in Norway 4 years after its implementation. Methods: A web-based questionnaire was sent to all accredited OHS asking about their experiences with the accreditation system. Responses were compared with a similar survey conducted in 2011. Results: The response rate was 76% (173/228). OHS reported that the most common changes they had had to make to achieve accreditation were: improvement of their quality assurance system (53%), a plan for competence development (44%) and increased staffing in occupational hygiene (36%) and occupational medicine (28%). The OHS attributed improved quality in their own OHS (56%) and in OHS in Norway (47%), to the accreditation process. Conclusions: The accreditation system was well accepted by OHS, who reported that it had improved the quality of their OHS and of OHS in Norway. The results are similar to the findings of a 2011 survey.