The diversity of child social skills development is not well detected among Asian countries. Culturally validated assessments are needed for practitioners to evaluate child social skills. This study tested the measurement invariance of the Social Skill Scale (SSS) across Japanese and Chinese samples and explored country differences in child social skills development. The SSS utilizes a widely used factor structure (assertion, self-control, and cooperation subdomains) and has established Japanese and Chinese versions. We conducted investigations with an identical process and materials with different language versions, collecting data from 931 Japanese kindergarten children (M
age
= 4.35, SD
age
= 1.07; 53.6% boys) and from 1130 Chinese kindergarten children (M
age
= 4.47, SD
age
= 1.00; 52.3% boys). We used multiple confirmatory factor analysis to test measurement invariance of the SSS and established the validity, reliability, and scalar measurement invariance for the first-order factor structure of the SSS across the two country samples. We also examined country differences on the associations between demographics, parenting practice, and child social skills development. We found that, compared to the Chinese sample, cooperation skills significantly increased more with age among the Japanese sample. However, spanking was negatively related to self-control skills development in both countries. Our findings contribute to the demonstration of the diversity of child social skills development and have important implications for assessing and developing child social skills using culture-specific strategies.