"Research Findings": The Ages & Stages Questionnaires: Social-Emotional, Second Edition (ASQ:SE-2) was translated and adapted into Traditional Chinese in Taiwan. A sample of 1,455 children, ranging from 42 months 0 days to 53 months 30 days old, reflecting the population sizes of different regions in Taiwan, completed the 48-month ASQ:SE-2. Data were analyzed by item response theory modeling. A multidimensional Rasch Partial Credit Model was chosen for data analysis. Differential item functioning (DIF) was used to explore the difference between the Traditional Chinese ASQ:SE-2 and the English ASQ:SE-2 (N = 3,005) administered in the U.S. Results indicated that (a) item fit statistics was between 0.88 -- 1.26 (M = 1.00, SD = 0.10), (b) difficulty was between -0.79 -- 3.19 (M = 2.06, SD = 0.84), (c) reliability was 0.79 for all items, 0.75/0.74 for Emotion/Sociality dimension, and (d) six out of 35 items (17.1%) with moderate to large DIF. "Practice or Policy": This research provided psychometric evidence for using the ASQ:SE-2-TC with a Taiwanese population. The promising psychometric findings encourage the further investment on validating ASQ:SE-2-TC. The cultural explanations can inform test developers to become aware of the potential influence from social values, parenting style, or childrearing practices.