Aim: To explore the evolution of antipsychotic polypharmacy (APP) and other psychotropic prescribing patterns during psychiatric hospitalisations, to detect characteristics associated with APP on admission and at discharge, and to examine clozapine prescribing patterns. Methods: Data on adult inpatients diagnosed with schizophrenia spectrum disorders were collected retrospectively from 6 Belgian hospitals. Results: Of the 516 patients included, APP prescribing increased significantly from 47.9% on hospital admission to 59.1% at discharge. On admission and at discharge, APP was associated with prior clozapine use (ORadmission=2.53, CI=1.1-5.84, ORdischarge=11.01, CI=4.45-27.28), treatment with a first-generation antipsychotic (ORadmission=26.79, CI=13.08-54.86, ORdischarge=25.2, CI=12.2-52.04), increased antipsychotic exposure (ORadmission=8.93, CI=5.13-15.56, ORdischarge=19.89, CI=10-39.54), and a greater number of hypno-sedatives (ORadmission=1.88, CI=1.23-2.88, ORdischarge=4.18, CI=2.53-6.91), and negatively associated with involuntary admission (ORadmission=0.31, CI=0.14-0.7, ORdischarge=0.3, CI=0.13-0.68). When using an alternative definition of monotherapy (i.e., including patients with an add-on low-dose antipsychotic for sleep disorders), alcohol use disorder (ORadmission=0.26, CI=0.13-0.54) and higher age (ORdischarge=0.53, CI=0.29-0.95) were negatively associated with APP, and living in a residential facility (ORdischarge=2.39, CI=1.21-4.71) and a higher daily dosage of benzodiazepines during the stay (ORdischarge=1.32, CI=1.03-1.69) increased the odds of being discharged on APP. Although 28.1% of patients were eligible for clozapine treatment, only 9.3% were being treated with clozapine on admission, and 11% at discharge. Seven of the ten patients with a new clozapine prescription were directly being prescribed a combination of antipsychotics, without a prior trial of clozapine monotherapy. Conclusion: Suboptimal prescriptions of antipsychotics in patients with schizophrenia persist after psychiatric hospitalisations and are associated with identifiable characteristics.