The experience of stress and associated coping responses are often described as playing an important role in the onset of schizophrenia and other psychotic disorders. Despite widespread acceptance of this model, there is little empirical evidence to support such a relationship. This is partly due to a lack of well-designed prospective studies of the onset of psychotic disorders that incorporate different aspects of the stress and coping process. The relatively recent development of validated and reliable criteria for identifying young people at high-risk (UHR) of developing psychosis has enabled the process of onset of psychotic illnesses to be studied more closely than was previously possible. It has also opened the way to the development and evaluation of preventive interventions. This longitudinal study aimed to compare the experiences of stress and coping between a UHR cohort (N = 143) and a group of young people without mental health concerns (HC group, N = 32). In addition, the contribution of stress and coping in the development of acute psychosis in a subgroup of the UHR cohort (UHR-P, n = 18) was also investigated.