The Preschool Early Numeracy Skills Test--Brief Version (PENS-B) is a measure of early numeracy skills, developed and mainly used in the United States. The purpose of this study was to examine the factorial validity and measurement invariance across gender of PENS-B in the Greek educational context. PENS-B was administered to 906 preschool children (473 boys, 433 girls), randomly selected from 84 kindergarten classrooms. A 2PL unidimensional and multidimensional item response theory analysis, using cross-validation procedures, were used to analyze the data. Results showed that responses to 20 items can be adequately explained by a two-dimensional model (Numbering Relations and Arithmetic Operations). Application of differential item functioning procedures did not detect any gender bias. Numeracy Relation comprises 16 items, which assess low levels of this latent trait. On the other hand, four items capture average levels of Arithmetic Operations. Total information curves revealed that both dimensions measure with precision only a small area of their underlying latent trait.