Teacher-child relationships and peer relationships are important predictors of children's loneliness. However, few studies have examined the potential and adverse relationship between teacher power and children's loneliness. Thus, we explicitly explored whether teacher power is related to children's loneliness and examined the potential moderating roles of interpersonal relationships (i.e., teacher-child relationships and peer relationships) in 888 Chinese children. Moreover, this study measured teacher power with children's figure drawings. The results showed that teacher power was significantly and positively related to children's loneliness, and both teacher-child relationships and peer relationships moderated the link between the two variables. Specifically, the adverse correlation between teacher power and children's loneliness was not significant among children with high-quality teacher-child relationships. Similarly, the negative effect of teacher power on children's loneliness was not found among children with a high level of peer relationships. Therefore, our results confirmed that the adverse relationship between teacher power and children's loneliness, and the protective roles of high quality of teacher-child relationships and high levels of peer relationships in this relationship. Potential implications and future research directions are discussed.