Objective: The COVID-19 pandemic has had a profound effect on global mental health, with one-third of infected individuals developing a psychiatric or neurological disorder 6 months after infection. The risk of infection and the associated restrictions introduced to reduce the spread of the virus have also impacted help-seeking behaviours. Therefore, this study aimed to determine whether there was a difference during the COVID-19 pandemic in the treated incidence of psychotic disorders and rates of admission to hospital for psychosis (including involuntary admission). Methods: Incident cases of first-episode psychosis in young people, aged 15 to 24, at an early intervention service in Melbourne from an 8-month period before the pandemic were compared with rates during the pandemic. Hospital admission rates for these periods were also compared. Results: Before the pandemic, the annual incidence of first-episode psychosis was 104.5 cases per 100,000 at-risk population, and during the pandemic it was 121.9 (incidence rate ratio = 1.14, 95% confidence interval = [0.92, 1.42], p = 0.24). Immediately after the implementation of restrictions, there was a non-significant reduction in the treated incidence (incidence rate ratio = 0.80, 95% confidence interval = [0.58, 1.09]), which was followed by a significant increase in the treated incidence in later months (incidence rate ratio = 1.94, 95% confidence interval = [1.52, 2.49]; incidence rate ratio = 1.64, 95% confidence interval = [1.25, 2.16]). Before the pandemic, 37.3% of young people with first-episode psychosis were admitted to hospital, compared to 61.7% during the pandemic (odds ratio = 2.71, 95% confidence interval = [1.73, 4.24]). Concerning the legal status of the admissions, before the pandemic, 27.3% were admitted involuntarily to hospital, compared to 42.5% during the pandemic (odds ratio = 1.97, 95% confidence interval = [1.23, 3.14]). Conclusion: There was a mild increase, which did not reach statistical significance, in the overall incidence of first-episode psychosis; however, the pattern of presentations changed significantly, with nearly twice as many cases presenting in the later months of the restrictions. There was a significant increase in both voluntary and involuntary admissions, and the possible explanations for these findings are discussed.