Emotion recognition (ER) involves understanding what others are feeling by interpreting nonverbal behavior, including facial expressions. The purpose of this study is to evaluate the psychometric properties of a web-based social ER assessment designed for children in kindergarten through third grade. Data were collected from two separate samples of children. The first sample included 3,224 children and the second sample included 4,419 children. Data were calibrated using Rasch dichotomous model. Differential item and test functioning were also evaluated across gender and ethnicity. Across both samples, we found consistent item fit, unidimensional item structure, and adequate item targeting. Analyses of differential item functioning (DIF) found six out of 111 items displaying DIF across gender and no items demonstrating DIF across ethnicity. The analyses of person measure calibrations with and without DIF items yielded no evidence of differential test functioning (DTF) across gender and ethnicity groups in both samples. [This is the online version of an article published in "Journal of Psychoeducational Assessment."]