This study aimed to examine the unique longitudinal role of theory of mind (ToM) on reading comprehension among primary school children, while controlling for other influencing factors. It also examined how this impact varies by grade, text genre, and processing level. A sample of 430 Chinese children in Grades 2, 4, and 6 was observed over a period of 6 months. For each grade, longitudinal hierarchical regression analyses were conducted to examine the unique contribution of ToM to reading comprehension across different text genres and processing levels. By controlling for variables such as reading frequency, decoding, vocabulary, nonverbal intelligence, listening comprehension, and executive function, ToM cannot predict the overall reading comprehension of children in Grade 2, but can predict it of children in Grades 4 and 6. For specific text genres, ToM predicted narrative comprehension in both Grades 4 and 6 and expository comprehension only in Grade 6. For specific processing levels, ToM predicted advanced comprehension in Grades 4 and 6 and basic comprehension only in Grade 6. Furthermore, ToM predicted advanced narrative and expository comprehension in Grades 4 and 6, and basic expository comprehension in Grade 6. These findings highlight the important role of ToM in reading comprehension development, particularly in the middle and upper stages of primary school. These results lay the foundation for further research on exploring the underlying mechanisms of the impact of ToM on reading comprehension and provide a social-cognitive perspective to enhance the development of reading comprehension.