Minimally verbal children with autism commonly demonstrate language dysfunction, including immature syntax acquisition. We hypothesised that transcranial direct current stimulation (tDCS) should facilitate language acquisition in a cohort (n = 10) of children with immature syntax. We modified the English version of the Bilingual Aphasia Test (BAT) to test only basic canonical subject-verb-object sentences. We tested syntactic accuracy after teaching then testing all vocabulary from the subsequent syntax test to ensure validity of syntactic scoring. We used scaffolding sentences for syntax training. All procedures were performed both before and after tDCS. Results demonstrated a large effect size of the difference between pre-/post-tDCS groups (p < 0.0005, d = 2.78), indicating syntax acquisition. Combining a modified BAT with tDCS constitutes effective modalities for assessment and treatment of immature syntax in children with autism. Future studies should explore the BAT for patients with an inability to use or understand language, in particular bilingual children with autism.