Objectives: Schizophrenia and associated illnesses account for a large proportion of mental illness burden and health care expenditures, with the majority of expense involving inpatient care. To date, the literature exploring factors associated with length of stay (LOS) and functional improvement during inpatient care is underdeveloped. In response, this study examined the association between patient characteristics, LOS, and functional improvement using Ontario Mental Health Reporting System (OMHRS) data from 2005 to 2015. Methods: The associations of patient characteristics (including key demographics, psychosocial variables, reasons for admission, and service use history) and 2 outcome measures (LOS and Global Assessment of Functioning [GAF]) were analysed with generalised linear mixed modelling (GLMM). From 2005 to 2015, a total of 48,498 episodes for distinct patients from 18 psychiatric hospitals and 57 general hospitals in Ontario were included. Results: For psychiatric and general hospitals, mean LOS was 96.6 and 20.5 days, and mean GAF improvement was 14.8 and 16.1, respectively. The majority of associations probed demonstrated a high degree of significance with similar patterns across general and tertiary facility contexts. Older age and more recent readmission following a psychiatric discharge were associated with longer LOS and less GAF improvement. Recent experience of adverse life events and substance misuse were associated with shorter LOS. Conclusions: While the findings of this exploratory cross-sectional analysis will require further inquiry with respect to validity and reliability, they suggest that a different service pathway is likely required for individuals with greater psychosocial challenge and extensive service use histories.