Background: Environmental factors and child characteristics play roles in the development of the theory of mind (ToM). Objective: This study investigates the impact of early rearing environment and child temperament on the development of the ToM by evaluating children under the care of social services at three different time points. Methods: This study included 112 children from institutions, 60 from care villages, 62 from group homes, and 51 from foster care. These children were tested at three time points with 8-month intervals. The age range of the children was 23-62 months at the first time point and 40-78 months at the third. Frustration and perceptual sensitivity as child temperamental characteristics were assessed with the Early Child Behavior Questionnaire and the Children's Behavior Questionnaire, while ToM was evaluated with a ToM task battery. Hierarchical linear modeling was performed to test the growth rate of ToM. Results: A three-way interaction (Frustration × Care Type × Time) revealed that children's ToM understandings significantly improved over time across most conditions for children with high frustration in both group homes and institutions as well as for children with low frustration in institutions. However, children with low frustration in group homes did not show significant improvement, emphasizing the potential protective role of frustration in institutional settings. Conclusions: This study demonstrates the importance of child characteristics and early rearing environment on the development of the ToM over time.