Objective: To compare the frequency and type of inpatient Parkinson’s medication errors reported through an incident report system versus those identified through retrospective case note review in a tertiary teaching hospital. Methods: A search of inpatient medication-related incident reports identified those pertaining to Parkinson’s medication. A discharge diagnoses search identified admissions for patients with Parkinson’s disease over the same time period. A retrospective case note and incident report review were performed to describe and quantify medication-related events. Key findings: Substantially, more medication-related problems were identified via case note review (n = 805) versus incident reporting system (n = 19). A significantly different pattern of error types was identified utilising case note review versus incident reporting, with case note review more likely to identify delayed dosing, and incident reports more likely to identify wrong dose or formulation administered errors. Conclusions: Retrospective incident report and case note review can be used to characterise medication administration errors encountered in an inpatient setting. Incident report review alone is insufficient in estimating error rates, and dual data collection methods should be used.