Background: Every year many organizations formulate a Code of Ethics (COE) but when it comes to implementing, it does not achieve the desired purposes. Ineffectiveness of CoES can stem from different factors and surely, one of them is bad formulation. This research was conducted to identify the barriers to effective formulation of CoES in one of the main state universities of medical sciences in Iran.Methods: A qualitative approach using thematic analysis in three stages of descriptive coding, interpretative coding and overarching themes was adopted to analyze data collected through 27 semi-structured interviews. This study was conducted in 2014-15 at Shahid Beheshti University of Medical Sciences, Tehran, Iran.Results: Totally 135 descriptive themes, 12 interpretive themes and 3 overarching themes emerged through analyzing interviews.Conclusion: In order to have an implementable COE, 12 barriers in three categories including “goal-setting”, “ap-proach” and “content” of the COE, must be removed. In “goal-setting”, real cultural conditions of the medical uni-versity must be considered. Moreover, the COE must be in response to perceived internal needs and its philosophy must be clear for all members of the university. Besides, the formulation “approach” of the CoES must be specialist, participatory and expertised. Finally, in “content”, different stakeholders with diverse values, levels of knowledge and needs should be carefully addressed. In addition, it is proposed to emphasize religious and humane values to encour-age participation of people. As a final point, the university should avoid imitation in the content of the COE, and con-ceptualize the values in motivating, inspirational and guiding words.