Several theories have been proposed to explain the presentation of intense interests in autism, including theories based on altered executive functioning, imbalanced reward sensitivity, and mitigating anxiety. These theories have yet to be examined in early childhood, yet knowledge of how intense interests emerge could provide insight into how best to manage intensity and support the many benefits of personal interests. Parents of 33 autistic and 42 non-autistic comparison children aged 3-6 years completed questionnaires to assess attention shifting and inhibitory control, responsiveness to rewards, and anxiety symptoms. Each behavior domain was examined for associations with parent-reported interest intensity. In autistic and comparison children, attention shifting was associated with interest intensity, where children with more difficulties showed more intense interests. In autistic children only, inhibitory control of attention also associated with interest intensity, where children with greater difficulties showed more intense interests. Reward and anxiety symptoms did not associate with interest intensity in either group, or across the sample. These findings suggest that, in early childhood, the presentation of intense interests is related to executive functioning regardless of diagnostic group. Helping children develop executive functioning skills may therefore be useful to assist with managing interest intensity in early childhood.