Objective: The current study intends to examine how young children understand intentionality of teaching with the theory of mind development, and how this understanding relates to their understanding of a teaching intention of an actual teaching activity. Methods: The theory of mind of 90 children aged 3-5 years and their understanding of intentionality of teaching were assessed. Additionally, children were randomly assigned to experimental condition in which the teaching intention of an activity (memory game) was explicitly revealed, or control condition in which the intention was not stated. Afterwards, their understanding of the teaching intention of the game was measured. The development of understanding of intentionality of teaching, and its relation to their theory of mind were examined. Whether age and understanding of intentionality of teaching predicted children's understanding of the teaching intention of the game was also investigated. Results: Along with the theory of mind development, children's understanding of intentionality of teaching also developed. Children's understanding of teaching intention of the game was related to their understanding of intentionality of teaching with age controlled. Children's recognition of the teaching intention of the game was predicted by understanding of the intentionality of teaching in the control condition, and it was predicted by both age and understanding of intentionality of teaching in the experimental condition. Conclusion: With the development of theory of mind, children come to understand that teaching involves a goal, and this development plays an important role in their appreciation of an actual teaching intention of the activity.