Background An organization's ability to identify and learn from opportunities for improvement (OFI) is key to increasing diagnostic safety. Many lack effective processes required to capitalize on these learning opportunities. We describe two parallel attempts at creating such a process and identifying generalizable lessons and learn from them. Methods Triggered case review programs were created independently at two organizations, Site 1 (Regions Hospital, HealthPartners, Saint Paul, MN, USA) and site 2 (University of California, San Diego). Both used a five-step process to create the review system and provide feedback: (1) identify trigger criteria; (2) establish a review panel; (3) develop a system to conduct reviews; (4) perform reviews; and (5) provide feedback. Results Site 1 identified 112 OFI in 184 case reviews (61%), with 66 (59%) provider OFI and 46 (41%) system OFI. Site 2 focused mainly on systems OFI identifying 105 OFI in 346 cases (30%). Opportunities at both sites were variable; common themes included test result management and communication across teams in peri-procedural care and with consultants. Of provider-initiated reviews, 67% of cases had an OFI at site 1 and 87% at site 2. Conclusions Lessons learned include the following: (1) peer review of cases provides opportunities to learn and calibrate diagnostic and management decisions at an organizational level; (2) sharing cases in review groups supports a culture of open discussion of OFIs; (3) reviews focused on diagnostic safety identify opportunities that may complement other organization-wide review opportunities.