Purpose: In the context of developmental trajectories, the association between adaptive functioning and core autism symptomatology remains unclear. The current study examines the associations of adaptive behavior with autism symptom sub-domains and with different facets of symptom expression. Methods: Participants include 36 children with a recent diagnosis of autism (33 males; mean age = 56.4 months; SD = 9 months). Families were recruited in the context of the Pediatric Autism Research Cohort (PARC) project. Parents filled out questionnaires at two time points, six months apart, regarding their child's autism symptoms and adaptive functioning. The longitudinal relationship between adaptive functioning and autism symptoms was investigated using Mixed Linear Model analyses: one assessing the relationship between general symptom levels and adaptive functioning, and another examining the associations between symptom frequency and impact with adaptive functioning. We conducted Pearson correlation tests at both time points to assess the associations between symptom sub-domains and adaptive functioning. Results: Findings showed that higher autism symptoms associated with lower adaptive behavior skills, and that this association remained stable over time. Autism impact scores did not significantly relate to adaptive skills, as opposed to frequency scores. Associations between adaptive functioning and autism symptom sub-domains strengthened over time. Conclusion: These findings suggest that adaptive functioning is associated with parent-report autism symptomatology, and that this association changes and, on average, becomes stronger over time. Findings may indicate that frequency and impact of symptoms have differential roles in the development of adaptive skills and are worthy of further exploration.