Sociologists have a rich history of studying the process of diagnosis and how people experience illness. Yet, the sociology of diagnosis and illness experience literatures have seldom been fully integrated. Instead, these literatures highlight one element of the illness journey, wherein scholars either primarily study diagnostic processes and categories or people’s illness experiences. Drawing on empirical studies that examine diagnosis and experiences of illness in varied settings (diagnosis during breast cancer surveillance, diagnosis and experience of autoimmune illness and incarcerated women’s experiences of diagnoses and illness), in this article we build on our concept of regimes of patienthood to explain how diagnostic journeys, and the relations and power dynamics that manifest during this time, shape the illness experience and practices of patienthood. We construct a classification of diagnostic processes grounded in our empirical research that span (1) sudden diagnoses, (2) long, changing diagnostic journeys and (3) diagnostic journeys marked by disbelief and denial of care. Our findings demonstrate how diagnostic journeys and illness experiences are intertwined, with different diagnostic pathways impacting how illness is experienced. Analysing these categories collectively demonstrates that diagnostic journeys, while heterogenous, shape the practices that patients develop to manage health conditions and navigate unequal health-care encounters.