A disturbance in the basic self-experience is theorized to play a central role in the development and experience of psychosis. Additionally, disturbed self-experience has been found to be broadly associated with the psychosis-related symptoms and the trajectories of these symptoms in people dealing with psychosis. Disturbed self-experiences are most commonly assessed with extensive structured interviews. These are not as easily implemented in practice. Hence, this study will use a self-report measure to screen for disturbed self-experience instead of a long structured interview. The data is part of the Genetic Risk and OUtcome of Psychosis (GROUP) study, a longitudinal multisite cohort study investigating risk and protective factors of the onset and trajectory of psychosis. Using a cross-sectional design, the associations between disturbed self-experience and the psychosis-related symptoms as well as obsessive and compulsive symptoms are investigated. Furthermore, using a longitudinal design, the associations between disturbed self-experience and the trajectory of the positive- and negative psychosis-related symptoms are investigated using linear mixed model regression analyses. Although the results did not fully support the hypotheses, there were some interesting findings. Self-reported lifetime disturbed self-experience was found to be associated with both positive and depressive psychosis-related symptoms. An ambiguous association with the negative psychosis-related symptoms was found. Furthermore, self-reported lifetime disturbed self-experience was found to be associated with the trajectory of the first-rank hallucinations over time. More specifically, self-reported lifetime disturbed self-experience was found to be associated with a remained susceptibility for developing hallucinations. This study concludes that self-reported lifetime disturbed self-experience seems to grasp some central element of the lived experience for some individuals dealing with psychosis.