The purpose of this study was to examine a gamified mobile application's effect on students' achievement, and whether the player types of the students predicted their achievement scores. A "pretest-posttest control group design" research was conducted with 65 undergraduate students taking a compulsory online course. In the study, a gamified mobile app was developed by the researchers and then applied within an online History I course. The results of the study showed no significant difference between the achievement scores of the Experimental Group and Control Group students. However, multiple linear regression analysis results showed that the Experimental Group's students' achievement scores were significantly predicted by the player types they used and their mobile app performance. It is argued, therefore, that this result underlines the importance of player type in designing effective mobile gamification apps for the purpose of learning. Suggestions for further studies are also provided.