Atomic physics teaching materials support student motivation to learn independently, guide, and direct students to master material with abstract characteristics. The teaching materials in blended learning can improve the tutorial system's interaction process in distance education with special characteristics. Universitas Terbuka students have various ages, professions, geographic location, social environment, and prior knowledge. This study aimed at analyzing the practicality and effectiveness of atomic physics teaching materials in blended learning to improve students' self-directed learning skills in the open and distance education system. This research involving 121 students spread across 12 regional offices in Indonesia. Analysis of the impact and consistency of students' self-directed learning skills used inferential statistics, then for data analysis, the improvement used N-gain. The results of the study showed the average tutorial feasibility using atomic physics teaching materials is the most dominant in explaining the teaching material thoroughly and is easy to understand. The average percentage of student activity results get the highest score on the activity of conducting discussions. The effectiveness analysis results showed the atomic physics teaching materials are proven to be effective in increasing students' self-directed learning. ANOVA obtained no significant difference from all test classes so that atomic physics teaching materials are effective for application to students who have low, medium, and high abilities. The process of practicality and effectiveness has implications for developing teaching materials for distance education systems that must pay attention to the tutorial process, learning management system, and several other components.