Purpose <p>While distinct pragmatic profiles are well-documented, grammatical abilities in autistic children show considerable heterogeneity: some exhibit grammatical difficulties, while others demonstrate age-appropriate grammar. Yet, one construction remains underinvestigated: passives of psychological/mental state verbs (“remember”, “love”). This is critical because young children are known to comprehend passives of agentive verbs (“kiss”, “push”) via an adjectival passive strategy before acquiring passive grammar. This strategy fails for psychological verbs, making them the true test of passive knowledge. Despite extensive research in typically developing (TD) populations and populations with other neurodevelopmental conditions, there is little research examining both types of verbal passive in English-speaking autistic children.</p> Methods <p>We examined comprehension of agentive and psychological passives, short and long, in 48 autistic children divided into those with co-occurring language impairment (ALI, <i>n</i> = 26, mean age: 11;10), and those without (ALN, <i>n</i> = 22, mean age = 11;02), compared to two control groups matched on non-verbal reasoning (TD-Match-ALI, <i>n</i> = 22, mean age: 5;11 and TD-Match-ALN, <i>n</i> = 22, mean age: 10;03), on a sentence-matching task.</p> Results <p>Children with ALN demonstrated age-appropriate performance across all constructions. In contrast, children with ALI performed at or below chance on both agentive and psychological passives, indicating absence of the adjectival strategy, and a profile distinct from all other groups including younger TD children.</p> Conclusions <p>The findings reveal distinct developmental trajectories: children with ALN show age-appropriate grammatical development, while children with ALI demonstrate fundamental syntactic impairments. These results highlight the importance of testing psychological verb passives to accurately identify grammatical difficulties that standardised assessments may miss.</p>