This study examined the dimensionality and measurement invariance of the Kindergarten Student Entrance Profile (KSEP), a brief screening tool designed for use as a universal school readiness assessment. Teachers rated the readiness of 10,031 children during the first month of kindergarten in four ethnically diverse, medium-sized school districts in central California. From the total sample, two random, independent subsamples were identified. First, S1 (n = 5,050) was utilized to conduct a CFA. Results yielded evidence supporting a two-factor structure encompassing children's social-emotional and cognitive readiness that is similar to previous studies examining the KSEP with less diverse student samples. Next, a series of confirmatory factor analyses (CFAs) were conducted using S2 (n = 4,981) to replicate the structure identified in the first CFA with an independent subsample and to test the measurement invariance of the KSEP across two sets of categorical variables: (a) gender and (b) parent education levels. Results from both sets of CFAs showed adequate fit to the two-factor structure, with the KSEP exhibiting measurement invariance across both gender and parent education levels. The results of this study provide additional psychometric evidence supporting the validity of the KSEP as a universal-level school readiness screener. Practical implications are also discussed.