["Autism Research, EarlyView. ", "\nABSTRACT\nChildren with autism spectrum disorder (ASD) frequently present with co‐occurring conditions that can influence autism symptom severity and complicate clinical management. However, studies with clinician‐confirmed diagnoses in non‐Western populations remain limited. In this multicenter cross‐sectional study, 1279 children aged 3–14 years with DSM‐5‐confirmed ASD were recruited from eight medical centers in China. Autism symptom severity was assessed using the Childhood Autism Rating Scale (CARS). Comorbidities were identified through clinical evaluation and specialized assessments, and developmental status was measured using the Gesell Developmental Schedule (GDS) and Wechsler Intelligence Scales. Associations with CARS scores were analyzed using generalized linear regression. Of participants, 96.6% had at least one comorbidity and 71.2% had multiple comorbidities. Common conditions were intellectual developmental disorders (IDD) (87.3%), food selectivity (45.3%), insomnia disorder (16.9%), developmental regression (15.6%), and behavioral problems (14.6%). Patterns differed by sex and age: gastrointestinal problem and sleep‐related interventions were more common in girls, whereas food selectivity was more common in boys. Older children showed higher rates of tic disorders, asthma, epilepsy, and offensive language, although these findings should be interpreted cautiously because the subgroup aged ≥ 6 years was small. In adjusted analyses, IDD, food selectivity, pica, insomnia disorder, and developmental regression were associated with higher CARS scores, whereas higher GDS and Wechsler scores were associated with lower CARS scores. In this Chinese cohort, comorbidities were prevalent and showed distinct sex‐ and age‐related patterns. Several comorbidities were associated with greater autism symptom severity, underscoring the importance of comprehensive developmental and medical assessment in ASD care.\n"]