["Autism Research, EarlyView. ", "\nABSTRACT\nAutism is a highly heterogenous neurodevelopmental condition that can significantly compromise the quality of life. For children showing atypical trajectories of development in their early years, early and intensive intervention has shown promise in enhancing the development of language, cognition, and social skills. Yet, marked variability in intervention response remains insufficiently understood. Characterizing this heterogeneity is essential for informing intervention strategies tailored to each child's developmental profile. The aim of the present work was to identify subgroups based on intervention response trajectories and investigate subgroup‐specific predictors of intervention outcomes. We analyzed longitudinal data from 125 children (15.2–42.0 months) receiving the Early Start Denver Model (ESDM) intervention over an average follow‐up period of 2 years (mean = 1.93 ± 0.25). Children gained an average of 17 points in Developmental Quotient (DQ), showed significant improvement in their adaptive skills and exhibited diminution of autism features. Using K‐means clustering, we identified 3 subgroups: Progressive Group A (PrGA; 36%), which had the highest baseline cognitive scores (82.3) and gained 17 DQ points in average throughout the intervention; Progressive Group B (PrGB; 41.6%), which showed significant developmental delay at baseline (mean DQ = 56.3) and gained 30 DQ points; and the Persistent Support Needs Group (PSNG; 22.4%), which also started in the range of delay (mean DQ = 47.7) and remained in this range throughout intervention (mean DQ = 41.1). Subgroup‐specific analysis revealed distinct patterns of baseline factors, including stronger adaptive skills and fewer autism features, associated with a higher cognitive outcome for PrGA and PrGB. Comparison of PrGB and PSNG further identified factors distinguishing children with similar levels of cognitive delay at baseline who nevertheless followed markedly different developmental trajectories. Lower levels of repetitive and restricted behaviors, stronger adaptive functioning, and greater cumulative intervention exposure characterized the PrGB group, suggesting that both child‐related and intervention‐related factors may contribute to variability in developmental outcomes.\n"]