The aim of this study was to validate a teacher rating scale (TRS-EN) for assessing early numeracy skills and for identifying mathematically low-performing 3- and 4-year-old children. Fifty-six preschool teachers assessed children's (3-year-olds = 127; 4-year-olds = 145) numerical relational, counting, and basic arithmetic skills. Construct validity evidence through confirmatory factor analysis supported both unidimensional and three-factor (i.e. numerical relational, counting and basic arithmetic skills) models. Also, TRS-EN demonstrated excellent internal consistency in both age groups. The teacher assessment scores corresponded well with standardized direct early numeracy measures, and predicted children's early numeracy skills six months later. The results clearly demonstrate that the TRS-EN can be used to assist teachers in assessing early numeracy skills, and help with identifying mathematically low-performing children.