The effects of educational computer games on achievement and computer self-efficacy of primary school children were the focus of this study. For this purpose, a computer game was utilized by a seventh grade class to learn about computer hardware in a computer course. The research design of the study was quasi-experimental type that included a control group. Experimental group spent two weeks in the game-based environment while the control group spent the same amount of time while learning through traditional didactic teaching method. Learners completed a computer self-efficacy scale and took an achievement test before and after their learning. Although both groups showed statistically significant learning gains after the treatments, there was no significant difference in the achievement and self-efficacy of students. Qualitative analysis showed that students enjoyed learning through the game-based learning environment, the environment supported students in their self-learning, reduced their stress, and afforded visual learning.