Autism research tends to exclude racially and ethnically minoritized autistic individuals, limiting the quality of the evidence base for characterizing and diagnosing language impairment in racially and ethnically minoritized autistic individuals. This systematic review examines reporting practices for participant socio-demographics in studies pertaining to language impairment in autistic school-age individuals using age-referenced assessments. This review was preregistered (PROSPERO: CRD42021260394) and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol. Database searches took place in August of 2021 in Linguistics and Language Behavior Abstracts, PsycINFO, PubMed, and the Directory of Open Access Journals, for publications during 1980-2021. Search terms included three essential concepts: autism, language, and age. Two coders independently screened and evaluated articles. Of qualifying studies (n = 59), 17 (29%) reported any information on participant race and ethnicity; in these studies, participants were at least 77% white. Thirty-two studies (54%) reported gender or sex; just 10 studies (17%) reported socio-economic status using multiple indicators. These findings indicate insufficient adherence to reporting guidelines and systematic exclusion of racially and ethnically minoritized. Future work must address replicable reporting and inclusion in autism research.