Purpose: The authors explored the cognitive mechanisms involved in language processing by systematically examining the performance of children with deficits in the domains of working memory and language. Method: From a database of 370 school-age children who had completed a grammaticality judgment task, groups were identified with a co-occurring language and working memory impairment (LI-WMI; n = 18) or specific language impairment (SLI) with typical working memory skills ( n = 60) and matched control groups. Correct and incorrect use of grammatical markers occurred either early or late in sentence stimuli, imposing a greater working memory load for late-marker sentences. Results: Children with SLI showed a lower preference for grammatical items than typically developing controls, regardless of error marker position. Children with LI-WMI demonstrated a performance pattern modulated by error marker position: Their preference for grammatical items was lower than typically developing controls for late but not early marker sentences. Conclusion: This pattern of results suggests that there are distinct and dissociable impacts of working memory and linguistic skills on metalinguistic functioning through a grammatical judgment task.