Having been shifted from traditional to online learning due to the community quarantine implementation, it is valuable to determine students' views about taking courses online. This research aimed to explore the teacher education mathematics major students' experiences with taking undergraduate mathematics courses online, precisely the benefits and challenges they encountered, and in what way they dealt with these challenges. The design used in this study is qualitative exploratory research by distributing open-ended questions to selected Bachelor of Secondary Education in mathematics students (N = 76) from a state university in the province of Bulacan, Philippines. Data were explored through thematic coding. The results indicated that among the gains of taking mathematics courses online, the students mostly gained from a convenient study time to access applicable web-based references and resources. In spite of unpredictable internet networks, limited teacher and peer interaction, vague learning content and discussions, some distractions, and a lack of satisfactory learning resources, independent and self-paced study paired and fired with enough self-motivation are suggested.