Polypharmacy is associated with the prescription of inappropriate medications and avoidable medication-related harm. A novel pharmacist-led intervention aims to identify and resolve inappropriate medication prescriptions in older adults with polypharmacy. To conduct a preliminary feasibility assessment of the intervention in primary care, testing whether specific components of the intervention procedures and processes can be executed as intended. The mixed-methods study was approved by the New Zealand Health and Disability Ethics Committees and public health agency. Patients from a New Zealand general practice clinic were recruited over 4 weeks to receive the intervention. The preliminary feasibility assessment included measures of intervention delivery, patient-reported outcome measures, and perspectives from ten patients and six clinicians. Data were analysed quantitatively and qualitatively to determine if a full-scale intervention trial is warranted. The study's progression criteria were based on established research and guided the decision-making process. The intervention met the study's progression criteria, including patient recruitment, retention, and adherence to the intervention procedures. However, several modifications were identified, including: (1) enhancing patient recruitment, (2) conducting a preliminary meeting between the patient and pharmacist, (3) supporting pharmacists in maintaining a patient-centred approach, (4) reviewing the choice of patient-reported outcome measure, (5) extending the 8-week follow-up period, (6) allocating more time for pharmacists to conduct the intervention. The study found the intervention feasible; however, additional development is required before progressing to a full-scale trial. This intervention has the potential to effectively reduce medication-related harm and improve outcomes for older adults with polypharmacy. ACTRN12621000268842 Date registered: 11/03/2021.