Background: Early childhood is a critical period of language development. Yet less is known about how language growth relates to the development of phoneme awareness and cognitive flexibility during this period. Aims: To examine the longitudinal associations between growth in phonological awareness and cognitive flexibility from 4 to 5 years in relation to three patterns of child language development: early, intermediate and late. Methods & Procedures: A sample of 439 four-year-old children were recruited and underwent repeated language, phonological awareness and cognitive flexibility testing to age 5. Children were classified into three language development groups based on their listening comprehension: early, intermediate and late. Group-based trajectory modelling was then used to examine the relations between cognitive flexibility and phonological awareness over time in relation to language outcome. Outcomes & Results: Early language developers were characterized by higher levels and greater improvement in language and phonological awareness skills between 4 and 5 years. Late language developers exhibited slower growth in expressive language development (in addition to lower receptive language at age 4). Intermediate and late language developers showed steeper growth in cognitive flexibility over the study. Conclusions & Implications: Findings affirm the interconnected nature of phoneme awareness, cognitive and language skill development in early childhood. Results suggest the importance of targeting skills across literacy and executive functioning/regulatory domains for children with language difficulties.