Best practices for how to respond are unclear when a medical error is discovered in a different system (inter-system medical error discovery or IMED). This qualitative study explored medical error professionals' views on disclosure, feedback, and reporting in these scenarios.We conducted semi-structured telephone interviews from January to September 2018 with 15 medical error professionals from 5 regions of the United States. Interview guides addressed perspectives on best practice, minimum obligations, and mediating factors with respect to IMED. Each transcript was coded independently by two investigators. Analysis followed the inductive approach of interpretive description.Medical error professionals expressed diverse views about minimum obligations and best practices for physicians when responding to IMED events. All cited practical barriers to disclosure, feedback, and reporting in these scenarios. There was general consensus that clear-cut, harmful errors should be disclosed to patients, and most advised investigation and feedback prior to disclosure. Respondents diverged in recommended best practices and thresholds for taking action. All noted the lack of guidance specific to IMED scenarios but differed in how they would extrapolate from more general guidance.While medical error professionals expressed consensus regarding obligations to disclose obvious errors, they differed on particulars. Guidelines or an algorithm could be very useful. Efforts to develop clear guidelines for IMED must take into account these factors, as well as practical and political challenges to communication about errors discovered across systems.