Children with autism spectrum disorders (ASD) experience high rates of anxiety, sensory processing problems, and gastrointestinal (GI) problems; however, the associations among these symptoms in children with ASD have not been previously examined. The current study examined bivariate and multivariate relations among anxiety, sensory over-responsivity, and chronic GI problems in a sample of 2,973 children with ASD enrolled in the Autism Treatment Network (ages 2-17 years, 81.6% male). Twenty-four percent of the sample experienced at least one type of chronic GI problem (constipation, abdominal pain, bloating, diarrhea, and/or nausea lasting three or more months). Children with each type of GI problem had significantly higher rates of both anxiety and sensory over-responsivity. Sensory over-responsivity and anxiety were highly associated, and each provided unique contributions to the prediction of chronic GI problems in logistic regression analyses. The results indicate that anxiety, sensory over-responsivity and GI problems are possibly interrelated phenomenon for children with ASD, and may have common underlying mechanisms.