This study investigates effects of syntactic complexity operationalized in terms of movement, intervention, and noun phrase (NP) feature similarity in the development of Aʹ-dependencies in 4-, 6-, and 8-year-old typically developing (TD) French children and children with autism spectrum disorder. Children completed an offline comprehension task testing eight syntactic structures classified in four levels of complexity: Level 0: no movement; Level 1: movement without (configurational) intervention; Level 2: movement with intervention from an element that is maximally different or featurally “disjoint” (mismatched in both lexical NP restriction and number); and Level 3: movement with intervention from an element similar in one feature or featurally “intersecting” (matched in lexical NP restriction, mismatched in number). The results show that syntactic complexity affects TD children across the three age groups, but also indicate developmental differences between these groups. Movement affected all three groups in a similar way, but intervention effects in intersection cases were stronger in younger than in older children, with NP feature similarity affecting only 4-year-olds. Complexity effects created by the similarity in lexical restriction of an intervener thus appear to be overcome early in development, arguably thanks to other differences of this intervener (which was mismatched in number). Children with autism spectrum disorder performed less well than the TD children although they were matched on nonverbal reasoning. Overall, syntactic complexity affected their performance in a similar way as in their TD controls, but their performance correlated with nonverbal abilities rather than age, suggesting that their grammatical development does not follow the smooth relation to age that is found in TD children.