A considerable body of research has shown that preschoolers who have a better understanding of emotions also have better social competence. In the present study, we focused on the potential roles that verbal ability and working memory may play in the relationship. A total of 187 4- to 6-year-old preschoolers completed: (i) the Test of Emotion Comprehension for emotion understanding; (ii) the Counting and Labelling test for working memory; and (iii) the Core Vocabulary scales of the WPPSI for verbal ability. Two teachers assessed each participant's social competence. The results showed that preschoolers' emotional understanding is a predictor of their social competence but verbal ability fully mediated the relationship. Furthermore, verbal ability positively predicted children's social abilities only when they also had superior working memory. These findings help us to understand how verbal ability and working memory affect the relationship between emotion understanding and social competence in preschoolers.