Objective: The ability to perceive that people have mental states such as thoughts, tendencies and beliefs, which might be different from ours or the fact, is known as the theory of mind. The present research aimed to study the development of theory of mind in deaf children, regarding the impacts of communication modes utilized by the parents, due to their hearing condition. It also studied the impacts of a low verbal false belief task (using a mute movie) in comparison with verbal tasks on deaf children’s performance in theory of mind, considering their limitations in receptive language. Method: The study was accomplished through a cross- sectional, developmental research design. The sample comprised 200 hearing and deaf children, the former with hearing parents and the latter with hearing/deaf parents, whose age ranged 3-18 years. Results: The results revealed that the deaf children of the first generation - i.e., those who have hearing parents, are intensively delayed in achieving the theory of mind, as compared with hearing children. However, the delay of the second generation deaf children - i.e., the deaf children with deaf parents in theory of mind development is considerably less than that of the first generation deaf children. The deaf children of deaf parents completely compensated for their delay in achieving theory of mind as they grew up. The average age of theory of mind development in hearing, the first, and the second generation deaf children were 4;6 , 11;0 and 7;6 (years- months) respectively.  The low verbal false belief tasks left no significant impact on children’s responses, regardless of their hearing condition. Conclusion: This research indicated that deafness brings about a substantial delay in development of theory of mind in deaf children. Lack of sign language acquisition in its critical period may cause such delay. As a communication mode, sign language facilitates interaction between the child and caregivers; enabling him/her to achieve information about mental states and mental representation, which, serve as prerequisites of theory of mind.