In this study, authors investigated the attachment of toddlers to their mothers and teachers and overall development based on their gender differences. The subjects of the study are 80 toddlers who are 25~36 months, their mothers, and teachers. We analyzed our data using t-test and two way ANOVA, and the results are as follows. First, the groups categorized by the types of the attachment between the toddlers and the mothers and the gender difference demonstrated the developmental distinctions, respectively. The interactional effects of the two factors emerged in communication and basic living. Second, the groups categorized by the types of the attachment between the toddlers and the teachers and the gender difference demonstrated the developmental distinctions, respectively. The interactional effects of the two factors emerged in gross motor skills, fine motor skills, and cognition. Third, with respect to the types of multiple attachments to mothers and teachers, toddler development brought meaningful differences. We discussed the importances of the attachment of the toddlers and the role of teachers based on the results of our research and proposed future projects and suggestions.