Occupational therapists working to a philosophy of client-centred practice will benefit from a reliable and well reviewed outcome measure to provide an evidence base. A systematic review of the literature was undertaken to evaluate worldwide publications on the use of the Canadian Occupational Performance Measure (COPM) to determine its impact on clinical practice in occupational therapy. A literature search strategy was deployed which resulted in a review of 64 articles. A themed analysis approach was used to integrate the results into linked and recurring themes. The focus of the systematic review was to concentrate on issues affecting clinical practice and the following were selected as key factors for consideration: negative and positive issues arising from the use of the COPM; impact on practice for the therapist, client, process and clinical work; and change initiatives for the therapist, client, process and clinical practice. A profile of all articles, which identifies where these factors are indicated, is presented as a summary guide to assist the clinician. The findings of the review indicated that the greatest impact of using the COPM was within clinical practice. Change initiatives indicated the need for further research in different clinical areas, as well as the continual development and need for more training of occupational therapists in the use of COPM as an outcome measure.