Introduction A paediatric cancer ward is a setting where pharmacists participate in direct patient care, acting as coordinators between the patient, caregivers and healthcare professionals. The aim of the study was to develop a Gap Finding Tool to support the setting up of a pharmaceutical care model at a Paediatric-Adolescent Cancer Ward. Methods The Standards of Practice for Clinical Pharmacy Services by the Society of Hospital Pharmacists of Australia Committee of Specialty Practice in Clinical Pharmacy (2013), the American College of Clinical Pharmacy (2014) and the European Association of Hospital Pharmacists (2014) were used to compile the Gap Finding Tool. The developed Tool was tested for content validity by a panel of experts and subsequently implemented over 2 months. Results The Gap Finding Tool comprised of nine sections with an average of eight statements each about pharmacy services that should be provided at ward level. For each statement, the rater indicates whether these contributions are provided. When the Tool was implemented at the Paediatric-Adolescent Cancer Ward, four major gaps were identified, namely, absence of a clinical pharmacist, lack of medicines information, vetting of chemotherapy prescriptions by pharmacist with limited access to patient data and lack of pharmacist-input on medicines availability. Processes requiring optimisation included discharge medication advice and documentation processes. Conclusion The developed Gap Finding Tool is an innovative tool which is versatile and can be used in ward or ambulatory clinical settings to identify gaps in pharmaceutical processes and services and compare national or regional practices to international standards.