BACKGROUND Long-acting injectable antipsychotics (LAIs) serve as a means to ensure medication adherence with the intention of improving outcomes for psychiatric patients. Evidence remains inconclusive regarding the impact of LAIs on relapses and psychiatric hospitalizations rates. METHODS The primary objective of this retrospective pre/post study was to determine whether initiating an LAI in a veteran population with schizophrenia, schizoaffective disorder, or bipolar disorder is associated with a decrease in the 1-year rate of psychiatric hospitalizations and emergency room (ER) visits. RESULTS For the combined primary endpoint, the 1-year rate of psychiatric hospitalizations and ER visits for patients with schizophrenia, schizoaffective disorder, or bipolar disorder was not significantly reduced after initiation of LAIs (n = 50, median [interquartile range]: 1.5 [1, 3] to 1 [0, 3], P = .055). However, the secondary endpoint of the 1-year rate of psychiatric hospitalizations was reduced (1 [0, 3] to 0 [0, 2], P = .026). Additionally, for those who received injections on a regular basis, the 1-year rate of hospitalizations and ER visits was significantly reduced (2 [1, 3] to 0 [0, 1.5], P = .009). CONCLUSIONS This retrospective study suggests that the initiation of LAIs is associated with a reduced rate of psychiatric hospitalizations as well as a reduced rate of psychiatric hospitalizations and ER visits for those patients who receive injections on a regular basis.