A low understanding of mathematical concepts can affect a student's learning process. In overcoming this problem, teachers must pay attention to students' self-efficacy. This quasi-experimental study aimed to determine the effect of the RME-based Krulik-Rudnick Heuristics learning model on understanding mathematical concepts regarding students' self-efficacy. The samples were obtained using the cluster random sampling technique. The data collection technique used was a test of description

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... ons. Hypothesis testing was performed using two-way ANOVA. The research found that Fa was F(0.05;1.45); therefore, H0A was rejected. Furthermore, Fb was lower than F(0.05;2;45), so H0B was accepted, and Fab was lower than F (0.05;2.45), so H0AB was accepted. It can be concluded that there was an effect of the learning model used on understanding mathematical concepts, there was no effect of self-efficacy (high, medium, and low) on mathematical concept understanding, and there was no interaction between learning models and self-efficacy (high, medium and low) on students' mathematical concepts understanding. It is recommended that further researchers apply RME-based Krulik-Rudnick Heuristics to other learning materials.