Objective: The study investigated factors associated with frequent (admissions), high (total length of stay) or heavy (frequent and high) hospital use, and with ongoing increased hospital use, for mental health conditions in a regional health district. Methods: A retrospective population-based study using longitudinal hospital, emergency department and community service use data for people admitted with a mental health condition between 1 January 2012 and 31 December 2016. Multivariate logistic regression models assessed the association of predisposing, enabling and need factors with increased, and ongoing increased, hospital use. Results: A total of 5,631 people had at least one mental health admission. Frequent admission was associated with not being married (odds ratio = 2.3, 95% confidence interval = [1.5, 3.3]), no private hospital insurance (odds ratio = 2.2, 95% confidence interval = [1.2, 3.8]), previous mental health service use (community, emergency department, lengthy admissions) and a history of a substance use disorder, childhood trauma, self-harm or chronic obstructive pulmonary disease. High and heavy hospital use was associated with marital status, hospital insurance, admission for schizophrenia, previous mental health service use and a history of self-harm. Ongoing frequent use was less likely among those aged 65 and older (odds ratio = 0.2, 95% confidence interval = [0.1, 1.0]) but more likely among those with a history of depression (odds ratio = 2.2, 95% confidence interval = [1.1, 4.4]). Ongoing high use was also associated with admissions for schizophrenia and a history of self-harm. Conclusion: Interventions targeted at younger people hospitalised with schizophrenia, a history of depression or self-harm, particularly with evidence of social and or health disadvantage, should be considered to improve long-term consumer and health system outcomes. These data can support policymakers to better understand the context and need for improvements in stepped or staged care for people frequently using inpatient mental health care.