Evidence on post-diagnostic support for people with young onset dementia is scarce. Previous studies have employed a problem-focused approach; however, evidence on ‘what works’ in real-life practice is essential to develop recommendations for service design and delivery. This study aimed to provide insight into ‘what works’ from the perspectives of people with young onset dementia and their supporters. We gathered free-text responses on positive service experiences via a UK cross-sectional survey. Inductive thematic analysis was used to identify the objectives of positive services and the needs these met. Follow-up interviews enabled in-depth insights from people with diverse diagnoses, ages and social situations. These were analysed using a template drawn from the survey. The 233 survey respondents gave 856 examples of positive support. Analysis of 24 follow-up interviews led to 16 themes clustered under three superordinate themes: ‘maintaining autonomy’, ‘being myself’ and ‘togetherness’. We found that positive services address the disruptions to sense of agency, selfhood and meaningful relationships that are experienced by those with young onset dementia. The study provides an in-depth understanding of the needs met by positive services for younger people with dementia. Our nuanced findings on good practice can inform age-specific guidelines for young onset dementia and indicate how personalisation can work in practice to help people with young onset dementia to maintain identity, autonomy and connections.