Aim: To examine interrater agreement and validity of the Functional Communication Classification System (FCCS) for young children with cerebral palsy (CP) aged 2 or 3 years. Method: Speech-language pathologist (SLP) and parent FCCS ratings for 31 children with CP (aged 2y, n=16; aged 3y, n=15; 18 males, 13 females) were examined for interrater agreement using a weighted Cohen’s kappa statistic. Relationships between FCCS (SLP) ratings and: (1) concurrent validity with the Language Use Inventory, a standardized pragmatic assessment for children aged 18 to 47 months, (2) gross motor and fine motor function, (3) associated impairments (visual and intellectual), and (4) primary expressive communication mode were examined using Spearman’s correlation coefficients. Results: Almost perfect interrater agreement between SLP and parent FCCS ratings were found (kw=0.94). Correlations with FCCS (SLP) were excellent for pragmatic function (rs=−0.83, p<0.001), intellectual function (rs=0.89, p<0.001), and primary expressive communication mode (rs=0.92, p<0.001). Correlations were good for gross motor function (rs=0.72, p<0.001) and visual impairment (rs=0.70, p<0.001) and fair for fine motor function (rs=0.53, p<0.002). Analysis was unwarranted for epilepsy (n=1 out of 31) and hearing-associated impairments (n=0 out of 31). Interpretation: The FCCS has excellent interrater agreement and validity for communication classification of children with CP aged 2 or 3 years and is highly suitable for surveillance and research purposes.