This study aims at the effect of teaching algebraic expressions in the algebra learning field of the 6th-grade Mathematics curriculum using educational games on students' academic success and attitudes. The research was carried out with a random sampling method in a public secondary school in the Black Sea Region of Turkey in the 2022-2023 academic year, with a total of 47 students, 23 in the experimental group and 24 in the control group, in two branches studying at the sixth-grade level. During the study, while no intervention was made to the control group, five educational games developed by the researcher were applied to the experimental group in addition to the existing curriculum methods. The mixed method, in which both quantitative and qualitative methods are used together, was used in the study. The research was carried out according to the explanatory design method, which is one of the mixed design types. Quantitative data were collected using the "Algebraic Expressions Achievement Test (CIBT)" developed by Oduncu (2020) in his master's thesis and the "Math Attitude Scale" developed by Önal (2013). A semi-structured interview form was used to collect qualitative data. The t-test method was used for independent samples of the obtained quantitative data. In the analysis of qualitative data, the descriptive analysis method was used. When the achievement and attitude post-test scores were compared in the analysis, a statistically significant difference was found in favor of the experimental group. As a result of the research, it can be said that using educational games in mathematics teaching positively affects academic achievement and attitude toward mathematics lessons. In the interviews with the students, they stated that they learned the subject of algebraic expressions better with the games played and understood the subjects better. According to this result, it is recommended that mathematics teachers design and use educational games in accordance with the grade level and subject.