Early intervention is a fundamental principle in health care and the past two decades have seen it belatedly introduced into the field of mental health. This began in psychotic disorders, arguably the least promising place to start. The steady accumulation of scientific evidence for early intervention has eventually overwhelmed the sceptics, transformed thinking in psychotic disorders and created an international wave of service reform. This paradigm shift has paved the way to a more substantial one: early intervention across the full diagnostic spectrum. 75% of mental illnesses emerge before the age of 25 years, and young people bear the major burden for those disorders that threaten the many decades of productive adult life. The paradox is that young people aged between 12 and 25 years have had by far the worst levels of access to mental health care across the whole lifespan. Health services are poorly designed, grossly under-resourced and typically unfriendly to, and untrusted by, young people. Furthermore, until recently there has been a quite striking lack of interest in this transitional age group from clinicians and researchers alike, who had unthinkingly accepted the paediatric–adult split of mainstream medicine without questioning its utility and validity for our field and our young patients. Over the past decade, however, a major shift in momentum has occurred to take early intervention in youth mental health more seriously. Here we discuss the recent advances and evidence supporting an innovative integrated model of youth mental health care and look to the future.