Purpose <p>Increasing numbers of autistic people are diagnosed later in life (i.e., over 35 years old), but little research has looked at how an autism diagnosis impacts on autistic people and/or loved ones of autistic people. This qualitative study aimed to understand the emotional and relational impact of a later life autism diagnosis.</p> Methods <p>Six autistic individuals (&gt; 35years) and six loved ones of autistic adults were interviewed and their results analysed using multi-perspective interpretative phenomenological analysis.</p> Results <p>Eight themes were generated; six themes across both samples: (1) positive changes, (2) autism stigma, (3) accepting and adjusting, (4) missed opportunities, (5) mental health difficulties, and (6) understanding autism creates a lens to see autism in others. Two themes were generated for autistic participants only: (7) feeling different, and (8) post-diagnostic support. Many autistic participants experienced mental health difficulties, felt different to others, and wondered whether an earlier autism diagnosis may have made life easier. Families were supportive, although adjusting to support autistic loved ones was difficult. Autism stigma affected autism disclosure for fear of rejection. An autism diagnosis increased sense-making, self-compassion, and confidence.</p> Conclusion <p>The findings highlight the importance of earlier assessments and post-diagnostic support for autistic adults and/or loved ones to overcome emotional and relational difficulties experienced pre-and-post-diagnosis.</p>