Due to the variety of research ethics and integrity training formats it may be challenging to use a common instrument to monitor and evaluate the development of competencies and learning progress as well as determine the effectiveness of the training. The present study scrutinises the use of learning diaries as one possible measure to evaluate the development of ethics competencies. The aim of the study was to increase understanding about how learning diaries capture development of research ethics and integrity competencies (...) of participants and explore the use of diaries as a measure of training effectiveness. In the evaluative case study, a micro-credential programme was used as the context of the study and data was analysed using deductive content analysis. As a result, we outline criteria for analysis to be used in ethics training programmes for learning diaries. Results indicated that learning diaries submitted in the forum format (compared to individual submissions) provide peer support, so learners display more content knowledge on high levels of reflection and understanding. Submitting learning diaries over a longer period and making submissions repeatedly can improve writing and reflection competencies. The quality of learning diary entries may also depend on learner characteristics, such as commitment and motivation. Keeping a learning diary can help retain obtained competencies over a longer period. The article ends with a set of recommendations for implementing learning diaries as one measure of evaluation. (shrink)