BackgroundMultiple-choice, true-false, completion, matching, oral presentation type questions have been used as an evaluation criterion in medical education for many years. Although not as old as other question types, performance evaluation and portfolio-like assessment types, can be called alternative evaluation, have been used for a considerable time. While summative assessment maintains its importance in medical education, the value of formative assessment is gradually increasing. In this research, the use of Diagnostic Branched Tree (DBT), which is used both as a diagnostic and feedback tool, in pharmacology education was examined.MethodsThe study was conducted on 165 students (112 DBT, 53 non-DBT) on the 3rd year of undergraduate medical education. 16 DBTs prepared by the researchers were used as data collection tool. Year 3 first committee was elected for implementation. DBTs were prepared according to the pharmacology learning objectives within the committee. Descriptive statistics, correlation and comparison analyzes were used in the analysis of the data.ResultsDBTs with the most wrong exits are DBTs entitled phase studies, metabolism, types of antagonism, dose-response relationship, affinity and intrinsic activity, G-protein coupled receptors, receptor types, penicillins and cephalosporins. When each question in the DBTs is examined separately, it is seen that most of the students could not answer the questions correctly regarding phase studies, drugs that cause cytochrome enzyme inhibition, elimination kinetics, chemical antagonism definition, gradual and quantal dose response curves, intrinsic activity and inverse agonist definitions, important characteristics of endogenous ligands, changes in the cell as a result of G-protein activation, ionotropic receptor examples, mechanism of action of beta-lactamase inhibitors, excretion mechanism of penicillins, differences of cephalosporins according to generations. As a result of the correlation analysis, the correlation value calculated between the DBT total score and the pharmacology total score in the committee exam. The comparisons showed that the average score of the pharmacology questions in the committee exam of the students who participated in the DBT activity was higher than the students who did not participate.ConclusionsThe study concluded that DBTs are a candidate for an effective diagnostic and feedback tool. Although this result was supported by research at different educational levels, support could not be shown in medical education due to the lack of DBT research in medical education. Future research on DBTs in medical education may strengthen or refute our research results. In our study, receiving feedback with DBT had a positive effect on the success of the pharmacology education.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12909-023-04342-w.