Individuals with autism spectrum disorder are more likely than typically developing individuals to experience a range of gastrointestinal abnormalities, including chronic diarrhea, constipation, food sensitivities, and abdominal pain. These gastrointestinal symptoms have been associated with higher levels of irritability and aggressive behavior, but less is known about their relationship with core autism spectrum disorder symptoms. We investigated the relationship between autism spectrum disorder symptom severity and gastrointestinal symptoms while accounting for three associated behavioral symptom domains (Irritability, Aggressiveness, and Specific Fears), in a sample of 176 children (140 males and 36 females) ages 2-7 years old with autism spectrum disorder. A large majority (93.2%) of the sample had at least one reported gastrointestinal symptom, and most (88.1%) participants had more than one gastrointestinal symptom. Various types of gastrointestinal symptoms were reported; the most common symptoms reported were constipation, food limits, gas/bloating, and stomach pain. After accounting for each associated behavioral symptom domain, repetitive behaviors and stereotypies were significantly associated with gastrointestinal symptom severity. Increased severity of autism spectrum disorder symptoms was correlated with increased gastrointestinal symptom severity. Social and communication difficulties were not significantly associated with gastrointestinal symptom severity after accounting for associated behavioral symptoms. Our findings replicate a previously described association between irritability and aggression and gastrointestinal symptoms. Furthermore, we found that repetitive behaviors, but not social or communication symptoms, are associated with gastrointestinal symptom severity, even after accounting for associated behavioral symptoms. This suggests that gastrointestinal symptoms may exacerbate repetitive behaviors, or vice versa, independent from other associated behavioral symptoms.