Clinical pharmacy services can be costly, and in resource-constrained healthcare services, should be prioritised towards patients with the greatest potential risks. At our health network, high-needs pharmacy criteria were developed to identify patients at greatest need of clinical pharmacy services. This retrospective study of 761 patients admitted to four hospitals in metropolitan Melbourne aimed to evaluate the ability of the high-needs pharmacy criteria to identify patients at increased risk of medication-related adverse clinical outcomes. Patients' clinical records were reviewed to determine if the patient met one or more elements of the high-needs criteria. Data on length of stay, 30-day readmission rate, medication-related problems, and medication-related incidents were obtained from the electronic records. Patients meeting one or more high-needs criteria had a longer length of stay (mean 6.7 days vs 3.1 days, p < 0.01), were more likely to be readmitted within 30 days (27% vs 16%, p < 0.01) and had a higher rate of medication-related problems (15% vs 7.6%, p < 0.01). The sensitivity of the high-needs criteria to identify patients with medication-related problems, medication-related incidents, or readmission within 30 days was above 80%. In conclusion, the high-needs pharmacy criteria identified older patients with longer length of stay who are at greater risk of 30-day readmission and medication-related problems.