The chewing experience acquired during ontogeny may lead to developing functional asymmetry of the masticatory apparatus, adversely affecting the maxillofacial region functions. The study aimed to assess asymmetry of the masticatory muscle activity in healthy individuals showing no dentofacial system dysfunction. In 17 volunteers (6 males, 11 females aged 18–23 years), motor functional asymmetry of the brain was assessed using standard motor tests, and surface electromyogram (EMG) of the masseter (MM) and temporalis muscle (TMs) was recorded on the right and left sides: in the resting state, with the maximum voluntary bite force, during deliberate unilateral mastication (alternately on the left and right sides), and bilateral voluntary chewing. Three groups with various asymmetry manifestations were distinguished and characterized based on the asymmetry indices of standard EMG parameters (integrated EMG (AIint), average amplitude (AIav), and chewing bursts duration (AId)) of the right and left muscles: 1) showing stable unilateral asymmetry of the MM and TM activity; 2) showing the “dynamic asymmetry” that was different for the MMs and TMs; 3) showing the “adaptive control”, when the muscle activity asymmetry was manifested adequately to the chewing test, and AIint of the MMs and TMs reached 40 ± 18% and 97 ± 20% during chewing on the left side, 242 ± 39% and 127 ± 32% during chewing on the right side, 115 ± 12%  and 115 ± 24% during bilateral chewing. The major significant between-group differences in AIint, AIav, and AId were reported for the MMs (the impact of the “group” factor on these indices was as follows: F = 11.0, p < 0.01; F = 5.72 and F = 3.73, p < 0.05; repeated measures ANOVA). Thus, in young adulthood, some people develop functional asymmetry of the masticatory muscles in the form of excessive predominance of electrical activity on one side of the face with changes in both amplitude and duration of the “chewing” EMG bursts.