Almost all autistic youths have special interests (SIs), which are focused, intense areas of passion and interest in a particular topic. Emerging research suggests that there are gender differences in SIs among autistic youth; however, commonly used measures that assess for the presence of SIs may not fully capture the granular nature of those differences between autistic boys and girls. Characterizing these differences is important for autism identification in girls, as SIs in autistic girls may often be overlooked by caregivers, teachers, and clinicians due to their more “typical” and more socially oriented content areas compared to autistic boys. This study therefore aimed to more fully characterize gender differences in SIs using a newly developed caregiver‐report measure of SIs (the Special Interests Survey; SIS). Caregivers of 1921 autistic youth completed the SIS. Analyses revealed many similarities between boys and girls; there were no gender differences in mean age SI onset, caregivers' perceptions of uniqueness or interferences of endorsed SIs, or duration of previous SIs. There were gender differences in endorsement of less than half (39%) of the SI categories measured, and there were minor differences in the number of endorsed current and past SIs. Categories with significant gender differences fell along typical gender lines (e.g., more boys interested in math and construction, more girls interested in animals and arts/crafts). This study extends the growing literature on SIs and gender differences in autism and has important implications for supporting autistic youth and their families.