Background: Many clinical educators feel unprepared and/or unwilling to report unsatisfactory trainee performance. This systematic review consolidates knowledge from medical, nursing, and dental literature on the experiences and perceptions of evaluators or assessors with this failure to fail phenomenon. Methods: We searched the English language literature in CINAHL, EMBASE, and MEDLINE from January 2005 to January 2015. Qualitative and quantitative studies were included. Following our review protocol, registered with BEME, reviewers worked in pairs to identify relevant articles. The investigators participated in thematic analysis of the qualitative data reported in these studies. Through several cycles of analysis, discussion and reflection, the team identified the barriers and enablers to failing a trainee. Results: From 5330 articles, we included 28 publications in the review. The barriers identified were (1) assessor’s professional considerations, (2) assessor’s personal considerations, (3) trainee related considerations, (4) unsatisfactory evaluator development and evaluation tools, (5) institutional culture and (6) consideration of available remediation for the trainee. The enablers identified were: (1) duty to patients, to society, and to the profession, (2) institutional support such as backing a failing evaluation, support from colleagues, evaluator development, and strong assessment systems, and (3) opportunities for students after failing. Discussion/conclusions: The inhibiting and enabling factors to failing an underperforming trainee were common across the professions included in this study, across the 10 years of data, and across the educational continuum. We suggest that these results can inform efforts aimed at addressing the failure to fail problem.