Purpose: To investigate associations between possible sleep bruxism (PSB) and sleep disorders in children/adolescents with autism spectrum disorder (ASD) as well as parental perceived stress. Methods: A cross-sectional study was conducted involving children/adolescents with ASD five to 19 years of age and their parents at a public institution that supports disabled people in the city of João Pessoa in Northeast Brazil. The parents answered a form addressing sociodemographic characteristics and medical data (schooling, income, age, sex, support level and use of medications). PSB was recorded based on the reports of the parents. Parental stress was investigated using the Perceived Stress Scale (PSS-10). Sleep disorders in the children/adolescents were investigated using the Sleep Disturbance Scale for Children (SDSC). Data analysis involved descriptive, bivariate and Poisson regression analyses (95% CI; p < 0.05). Results: Fifty children/adolescents with ASD participated in the study. Boys accounted for 84.0% of the sample (n = 42). PSB in the children/adolescents was reported by 28.0% of the parents. The mean parental PSS-10 score was 20.3 ± 8.5 and the mean SDSC score was 48.8 ± 17.5. The adjusted Poisson model revealed associations between PSB and higher levels of perceived stress of the parents (PR = 1.05; 95% CI: 1.01–1.09), sleep breathing disorders (PR = 1.14; 95%CI: 1.05–1.24) and sleep-wake transition disorders (PR = 1.16; 95%CI: 1.00-1.36; p = 0.044). Conclusion: The occurrence of PSB in children and adolescents with ASD was associated with higher levels of parental stress, higher scores for sleep breathing disorders and sleep-wake transition disorders.