This research examined happiness with online learning among 2,190 undergraduate students at Suan Dusit University (SDU), who studied online in the first semester of the 2021 academic year. The data were collected from online happiness assessment forms completed by the SDU students. Frequencies, percentages, means, and standard deviations were calculated, and t-tests and one-way ANOVA were performed to analyze the data. The results indicated that students' overall happiness with their online learning was at a moderate level. The students were also satisfied with their studies at a moderate level. They were also moderately proud of the university and were comfortable with online learning, especially regarding the instructors, online instruction, the instructional activities, and lesson content. Students of different genders all enjoyed learning with the online instructional system, as arranged by SDU, at the same level. However, students from different majors, different years, different faculties or schools, different learning campuses or centers, and with different average monthly allowances, enjoyed their online learning at SDU differently.