Background: Guidelines are usually developed using systematic literature reviews. Expert opinion plays a key role but can be difficult to incorporate. The objective of this study was to develop a national consensus of expert opinion on the management of Locally Advanced Breast Cancer (LABC) and subsequently identify gaps in knowledge translation in current practice. Methods: 361 Canadian oncologists were subdivided into LABC experts (n = 83) and non-experts (n = 278). Experts were surveyed with a modified Delphi protocol to establish consensus. A systematic literature review was performed and compared to expert opinion. Non-experts were then surveyed with a 29-item questionnaire to determine current practice patterns. Z test was used to assess discordance. Results: Response rate for the expert survey was 61% (51/83). Consensus was achieved in all key aspects of care and was concordant to published literature in areas of: clinical assessment with caliper at each cycle, option of lumpectomy if good clinical response, radiotherapy to loco-regional lymph nodes, and no further adjuvant chemotherapy outside of clinical trial if residual disease found at time of surgery. Response rate for the non-expert survey was 50% (140/278). Areas of discordance are highlighted below. Conclusions: A national practice consensus guideline reflective of current evidence and expert opinion has been developed on the management of LABC. Differences in expert opinion and current practice have been identified as targets for knowledge translation interventions (KTIs) that may improve quality of care and resource utilization. Further exploration of KTIs to address identified gaps is warranted.