The American Academy of Pediatrics recommends that children be screened for autism at 18 and 24 months. It is unknown whether a positive screen usually represents the first developmental concern or is typically preceded by other developmental and/or medical concerns. This study evaluated the proportions of toddlers (M = 18.69 months) who screened positive for autism for whom caregivers or providers had prior concerns, the nature and timing of prior concerns, and their relationship with family characteristics. The electronic health records of 242 children who screened positive using the Modified Checklist for Autism in Toddlers--Revised with Follow-up during routine well-child visits were reviewed. Among toddlers who screened positive for autism, the majority (79.34%) had a documented prior motor, language, and/or autism concern. The presence of specific concerns was associated with earlier timing and higher Modified Checklist for Autism in Toddlers--Revised with Follow-up scores. Prior medical concerns were common, such as sleep (23.14%) and gastrointestinal (66.12%) problems. A positive autism screen often occurs in the context of pre-existing concerns. Thus, screening can provide providers with an opportunity to contextualize feedback about autism in the context of prior developmental and medical concerns.