While the most prevalent means to measure the effectiveness of research ethics and integrity training formats is using learners’ self-assessment, there is a need for reliable and feasible self-assessment tools to evaluate the level of understanding. The aim of the study was to design a reliable tool and test its accuracy in various training contexts. The current study utilized a design-based research (DBR) approach. Data were collected from 401 participants in training sessions and ten experts were involved in tool evaluation. (...) The results indicate that in the context of research ethics and integrity learners can quite accurately (more than 80%) evaluate their level of understanding with the designed self-reflection form. The research revealed that participants who assessed themselves to have higher levels of understanding or who used the tool several times were more likely to provide well-elaborated descriptions of their learning that matched their indicated level of understanding. (shrink)