This study examined the structure of the Best Start Kindergarten Assessment (Best Start) of literacy and numeracy, with the aim of confirming a two-factor measure of attainment at school entry comparable in structure to standardised measures of literacy and numeracy administered in later school years. Administrative data from the 2009 Best Start were obtained from the New South Wales Department of Education for 37,734 children aged ~5 years (i.e. as they entered their first year of compulsory schooling) as part of the New South Wales Child Development Study. Exploratory and confirmatory factor analyses were performed on the 11 Best Start scales using a split half methodology, with the findings supporting a two-factor solution underpinning literacy and numeracy attainment. The availability of this two-factor Best Start measure of literacy and numeracy at school entry, which precedes the repeated national assessments conducted later in the primary and high school years, facilitates research to examine pathways of academic performance over time.