Despite their high prevalence and clinical importance in autism, unusual and restricted interests remain under-researched and poorly understood. This study aimed to characterize the frequency and type of interests in autism by coding caregivers' open-ended responses in a sample of 237 autistic children and adolescents (M[subscript age] = 8.27 years, SD[subscript age] = 4.07; range: 2.08-18.25 years). It further aimed to explore the effects of age, sex, cognitive functioning and social and communication deficits on the number and type of interests. We found that 75% of autistic youth had at least one interest and that 50% of those children showed two or more different interests. The most frequent interests were sensory-based (43%), with a majority of these interests relating to the visual modality. Interest within vehicles/transportation, fictional characters, television/digital versatile disk/movies, computers, and video games, constructive, mechanical objects, animals and plants, and attachment to specific objects were also prevalent. Logistic regression showed that being male, having a co-occurring intellectual disability and having more severe social and communication impairments were associated with a higher probability of having one or more restricted interests. Sex was significantly associated with the type (X[superscript 2] = 37.52, Phi = 0.37, p = 0.021) of restricted interests, with females showing a significantly higher percentage of creative interests and males significantly higher percentage of interest in characters, vehicles/transportation, computers/video games, mechanical objects and constructive interests. Theoretical and measurement implications are discussed.