AimTo investigate spoken language comprehension (SLC), singleāword comprehension (SWC), functional communication development, and their determinants, in children with cerebral palsy.MethodThis was a prospective cohort study in the Netherlands spanning 2āyears 6 months. The main outcomes were SLC and SWC, assessed by the ComputerāBased instrument for Low motor Language Testing (CāBiLLT) and the Peabody Picture Vocabulary TestāIIIāNL (PPVTāIIIāNL) respectively; and functional communication, measured by a subscale of the Focus on the Outcomes of Communication Under Sixā34 (FOCUSā34). Linear mixed models were used to determine developmental trajectories, which were compared with norm and reference data. Potential determinants, for example intellectual functions, speech production, functional communication level (classified with the Communication Function Classification System, CFCS), and functional mobility, were added to assess their effects.ResultsChildren with cerebral palsy (nā=ā188; mean age 59āmonths, range 17ā110) were monitored for 2āyears 6 months. Developmental trajectories for SLC (CāBiLLT) and SWC (PPVTāIIIāNL) were nonlinear; those for functional communication (FOCUSā34) were linear. Compared with norm and reference groups, significantly delayed SLC, SWC, and functional communication development were found. Determinants for SLC and SWC were intellectual functions and functional communication level (CFCS); and for functional communication development (FOCUSā34), speech production and armāhand functioning.InterpretationChildren with cerebral palsy showed delayed SLC, SWC, and functional communication development compared with norm and reference groups. Remarkably, functional mobility was not associated with the development of SLC, SWC, or functional communication.