The present study investigated gender differences in social mastery motivation, vocabulary knowledge, behavioral self-regulation, and socioemotional skills and examined the relationships among this knowledge and these skills by gender. Participants were 134 Chinese children (68 boys, M age = 3.80; 66 girls, M age = 3.89) and their parents recruited through local kindergartens' parent groups. The children were administered measures of social mastery motivation, vocabulary knowledge, behavioral self-regulation, and nonverbal intelligence. Parents reported their education level and children's socioemotional skills. Research Findings: Results revealed that boys exhibited more social mastery interactions than girls, and girls showed better behavioral self-regulation and socioemotional skills than boys. Girls with higher social mastery interaction frequency demonstrated better vocabulary knowledge and socioemotional skills, whereas boys with higher social mastery interaction frequency showed lower behavioral self-regulation. Boys, who showed more positive affect during social mastery interactions, tended to have better expressive vocabulary, which facilitated their behavioral self-regulation. Practice or Policy: Findings highlight social mastery motivation as a potential factor that facilitates children's early development, but it may contribute to boys and girls in different ways.