Children who are deaf or hard of hearing (DHH) show delays in Theory of Mind (ToM) development. Complement sentences such as “Eliane says that Santa Clause exists” influence ToM performance. Can a training program targeting sentential complements enhance ToM? Twenty-one French-speaking DHH children (Mage = 8 years 11 months) with delays in ToM and sentential complements completed a first series of tests (T0). Children were tested again to control for maturation effects (T1), after which they were included in a 6- to 8-week training program targeting complements with verbs of communication. Post-training tests (T2) assessed if the training yielded improvements on complements (direct effect) and ToM (transfer effect). While no gains were noted in the absence of training (at T1), results indicate post-training (T2) improvements in complements and ToM tasks, suggesting that the acquisition of sentential complements provides a tool to represent subjective truths and boosts ToM reasoning in DDH children.