What is known and Objective: Older hospital inpatients are often prescribed complex multi-drug regimens; increased regimen complexity is associated with poorer medication adherence and treatment outcomes. There has been little research into methods for reducing regimen complexity. The objective of this study was to explore the feasibility of incorporating medication regimen simplification into routine clinical pharmacist care for older hospital inpatients and identify barriers to regimen simplification at a major teaching hospital. Methods: Following an educational intervention, clinical pharmacists were encouraged to minimize regimen complexity for their patients by identifying potential simplifications during routine medication regimen reviews (e.g. medication chart reviews, discharge prescription reviews) and discussing these changes with hospital doctors and patients. Pharmacists completed a data collection form for patients aged 60 years or above discharged from their wards during the study period (n = 205; mean age, 81A?3 years), indicating whether they had reviewed the patient s medication regimen complexity (and if not why), whether any changes to simplify the regimen were identified, and whether changes were successfully implemented (and if not why). Results and Discussion: Pharmacists reviewed medication regimen complexity for 173/205 (84A?4 ) patients and identified 149 potential changes to reduce regimen complexity for 79/173 (45A?7 ) reviewed patients. Ninety-four (63A?1 ) changes were successfully implemented in 54/205 (26A?3 ) patients. Regimens were simplified more often for patients discharged from subacute aged care (geriatric assessment and rehabilitation) wards compared with acute general medicine wards. The most commonly cited reason for not reviewing regimen complexity and not implementing identified simplification-related changes was lack of time . Non-acceptance of pharmacist recommendations by patients or doctors were other common reasons for not implementing changes. What is new and Conclusion: This is the first study to explore pharmacist-led medication regimen simplification and barriers to regimen simplification in the hospital setting. It demonstrates that simplification of older inpatients regimens is feasible when training in regimen simplification is provided. The main barrier to regimen simplification appears to be lack of pharmacist time.