Research involving monolinguals has demonstrated that language impairment can be noticed in the early years and tends to persist into adolescence. More recently, research has begun to address the challenges of identifying and treating Developmental Language Disorders (DLD) in English Language Learners (ELLs). Developmental patterns of DLD are not necessarily consistent over time, and we hypothesized that some monolinguals and ELLs go "under the radar" in lower grades but their language difficulties become more pronounced in later years, as syntactic demands increase, hence "late-emerging DLD". This longitudinal study examined (a) the existence of late-emerging DLD in Grades 4-6 in English-speaking monolinguals and ELLs, and (b) the Grade 1 and 3 cognitive and language profiles that predict late-emerging DLD. This study involved monolinguals (n = 149), and ELLs (n = 402) coming from diverse home language backgrounds. Cognitive (working memory, phonological short-term memory, processing speed), language (vocabulary and syntax), and word reading skills were assessed annually from grades 1 to 6. Separate parallel analyses in the monolingual and ELL samples confirmed that late-emerging DLD exists in both groups. In comparison with their typically developing peers, late-emerging DLD can be identified as early as Grade 1 based on poorer performance on phonological awareness, naming speed, and working memory.