Background: Service culture refers to the practices, views and values within service organisations. Developing positive cultures has been thought imperative to improving social care, though day services and their cultures remain an under-researched area. For many autistic people with profound learning disabilities, day services are the sites at which they orientate their Monday-Friday adult lives and so service cultures are fundamental to the way they experience adulthood. It was thus the purpose of this study to explore day service culture through the perspectives and experiences of this group. Methods: This study took a phenomenological approach involving extended participatory observations with an autistic person with profound learning disabilities at their day service, as well as broader ethnographic work within this context. Data was analysed through theory-led thematic analysis. Findings: The study found that autistic people with profound learning disabilities contribute their customs and values to service culture in everyday life and that space, time and place were important in this endeavour. It highlighted how these customs and values could be adopted or challenged by the service, its staff and their established culture. Conclusion: It is argued that positive service cultures are ones in which day services acknowledge and respond to the views and values of autistic people with profound learning disabilities. A potential framework is discussed to support services with this aim.