The aim of this study is to explore the correlation between the intrinsic motivation of fourth-grade primary school students in mathematics and their academic performance in mathematics while considering the factor of their favorite subject. The goal is to determine whether there is a difference in intrinsic motivation and achievement in terms of their favorite subject. A convergent parallel design was used in the study. The sample of the research consisted of 142 students who participated in face-to-face research in the city center and districts of Çanakkale in the 2019/2020 academic year, as well as 109 students who participated in online research in the 2020/2021 academic year. The study group was comprised of 10 students, for whom the data were collected in face-to-face sessions, and 12 students who participated in the research online. The data for this study were collected using the "Mathematics Lesson Motivation Scale" developed by Balantekin and Oksal (2014), as well as the "Mathematics Lesson Achievement Test", "Demographic Form", and "Semi-Structured Interview Form" developed by the researchers. When examining the results of the research related to intrinsic motivation, significant differences were observed in both online and face-to-face data collection, with respect to the obtained data. According to the qualitative data obtained from this study, those students with intrinsic motivation were expected to perform well in the course. However, it was observed that regardless of their academic performance, all students were motivated towards the course. As a contrasting result, it was determined that the most successful student in the school did not possess intrinsic motivation towards the course.