<p>There have been few studies on the effect of Angle’s classification of first molars on the difference in masticatory performance between the habitual chewing side (HCS) and the non-habitual chewing side (NHCS) in young people with healthy dentition. Thus, this study aimed to investigate the masticatory performance of the HCS and NHCS in individuals under 20&#xa0;years of age with complete permanent dentition, divided into Class I and non-Class I first molar relationship groups (Class I group and non-Class I group). The participants were first- and second-year female dental hygiene students at the Nippon Dental University College in Niigata in 2024. Twenty-eight participants were classified into two groups based on the Angle’s classification: Class I and non-Class I first molar relationships. HCS was determined using the cotton roll test, and masticatory performance was evaluated using glucose-containing gummy jelly. Participants were asked to chew a gummy jelly for 20&#xa0;s on the HCS, and the amount of glucose extracted was measured as an indicator of masticatory performance. The same measurement was then performed on the NHCS. In the Class I group, the median (interquartile range, IQR) of the HCS was 202.00 (186.00–231.00) mg/dL and of the NHCS was 191.00 (120.50–238.50) mg/dL. In the non-Class I group, the HCS was 188.00 (140.00–225.00) mg/dL and the NHCS was 167.00 (156.00–235.00) mg/dL, respectively. A significant difference between the HCS and NHCS existed in the Class I group (<i>p</i> = 0.041), whereas not in the non-Class I group (<i>p</i> = 0.423). The null hypothesis of the study—that there is no difference in masticatory performance between HCS and NHCS, regardless of Angle’s classification of the first molar relationship—was rejected.</p>