Preferred interests are characteristic of autism spectrum disorder and are reported by parents starting at an early age. However, limited research has explored the presentation of preferred interests in toddlerhood. Previous literature suggests that both the intensity and type of preferred interests held by autistic individuals differ from those held by peers with developmental delay and no diagnosis and that autistic interests are more unusual in nature. While preferred interests are seen in typical child development, previous research suggests that the presence of preferred interests in children with no diagnosis declines with age. Literature also indicates that the sex and cognitive ability of autistic children influences preferred interests. Identification of early preferred interests commonly held by autistic toddlers could serve as a useful clinical indicator of future diagnosis. This article explored whether diagnostic group, age, sex, and cognitive ability predict the likelihood that parents reported preferred interests in children aged 12–36 months with diagnoses of autism, developmental delay, and those with no diagnosis. Additionally, we explored potential diagnostic group differences in interest type. Results suggest that diagnostic group, but not age, sex, or cognitive ability, predicts the likelihood that parents report preferred interests. No differences in the type of interests among diagnostic groups were identified. These results support the use of preferred interests as an early sign of autism but suggest that interest type may not be a helpful clinical indicator of autism in toddlerhood.