Purpose This study aims to investigate whether epistemological assessment is a suitable approach to evaluate students’ learning of dietary knowledge via the use of an augmented reality (AR) information system. Students’ perceived dietary knowledge was compared before and after learning with the AR system. Two major questions were addressed: Did students improve their understanding of dietary knowledge after the use of AR information system? Did students gain more appropriate understanding of dietary knowledge after the use of AR information system? Design/methodology/approach A mixed-methods approach was used in the study. The mobile AR system was used among 65 volunteered non-nutrition-major college students recruited in campus. For promoting epistemological development of personal dietary knowledge, students practiced with life experiences to access daily dietary information. Pre- and post-tests of students’ understanding of dietary knowledge were compared. Interviews with 20 students were used for gathering in-depth research data to analyse students’ epistemological understanding of dietary knowledge. Findings The epistemological assessment indicated an improvement in learning after the use of the AR system. Students gradually gained awareness of dietary knowledge and changed their perceptions of their dietary behaviours. Epistemological approaches to the analysis of students’ conceptual change in dietary knowledge revealed a significant increase in the mean nutritional concepts (p < 0.01) and a decrease in their mean misconceptions (p < 0.001) after learning via the mobile nutrition monitoring system. Learning assessment of 65 students also indicated a significant increase from the post-test after learning with the system (p < 0.0001). Research limitations/implications This study might have its limitations, as it only assessed learning using a pretest-posttest design for a specific learning context over a short period of learning time. The use of interviews based on the epistemological approach might have its limitations in the interpretations of the phenomenon. Future implementations can also be extended to different populations to promote self-monitoring dietary behaviours. Originality/value The findings of this study will contribute to the application of AR in learning about dietary knowledge. The research involving in-depth observation of students’ learning relevant to personal nutritional information needs via mobile AR might provide potential contributions to dietitian professionals and health education.