Aims: The current study aimed to validate the relationship between sensory characteristics and sleep dynamics among children with autism spectrum disorder (ASD) using an actigraph, which is an objective assessment device used for sleep monitoring. Methods: A total of 40 children (age range, 3-6 years) participated in this study (n = 20, with ASD and n = 20, age-matched children with typical development [TD]). We examined sleep dynamics using actigraph for 7 consecutive days, and the relationship between sleep parameters and sensory characteristics was analyzed using the Japanese Version of Sensory Profile (SP-J). Results: Significant differences were observed in terms of activities per minute during sleep (p = 0.02), sleep efficiency (SE) (p = 0.005), and wake after sleep onset (WASO) (p = 0.02) between the two groups. In the ASD group, significant positive correlations were observed between activities per minute during sleep and low thresholds for Vestibular Sensory stimuli (p = 0.046) and Oral Sensory stimuli (p = 0.006) using the SP-J. Based on a multiple regression analysis, the activities per minute during sleep were associated with low thresholds for Oral Sensory stimuli (b = 0.51, t = 2.29, p = 0.03), but not with other factors, in the ASD group. Conclusions: The current study showed that atypical Vestibular and Oral Sensory modulation may be a risk indicator for high activities during sleep among preschool children with ASD. Thus, whether the interventions for these sensory characteristics are effective in improving sleep quality, daytime activities, behaviors, and cognitive functions in this group of children must be considered.