The current study examines the relationship between bilingual children's dual language experience (i.e. language input, language output and vocabulary proficiency), and their social-emotional and behavioral skills. Data were analysed from 805 Singaporean bilingual preschoolers (ages 4; 1-5; 8 years), who are learning English and either Mandarin (n = 551), Malay (n = 105), or Tamil, (n = 149). A parent questionnaire and standardized vocabulary tests were used to assess children's bilingual language environment and vocabulary knowledge. Children's social-emotional and behavioral skills were evaluated by teachers using the Strengths and Difficulties Questionnaire. A series of variables which might influence social-emotional and behavioral skills (e.g. gender, non-verbal IQ, SES, and emotion recognition) were controlled and mixed-effects models were used to conduct data analysis. Results demonstrated that children who had larger bilingual receptive vocabulary and had frequently spoken both languages for a longer time had better social-emotional and behavioral skills. Gender and emotion recognition ability were also found to be significantly related to children's social-emotional and behavioral skills. Such findings held true for children across different Mother Tongue language backgrounds. This suggests that a good language environment for bilingual children should be promoted not only for the sake of their early language development, but also because of the potential benefits to their social-emotional and behavioral skills.