Purpose: Children with developmental language disorder (DLD) experience difficulties with an important Theory of Mind milestone, namely, false belief (FB) reasoning. Their FB success relates to mastery of a linguistic structure that is also challenging for them, namely, sentential complements (e.g., "Claire says/thinks [that Santa Claus exists]"). Training typically developing (TD) children on complements has been shown to boost complements and, in turn, enhance FB, but such training has never been explored with children with DLD, which is the aim of the current study. Method: Fifty French-speaking children followed a novel training program: 30 with DLD (M[subscript age] = 7;3) and 20 TD (M[subscript age] = 4;3). They engaged in iPad applications targeting complementation with verbs of communication (e.g., "say," "shout," "answer") during eight to 12 sessions lasting 30 min. Training commenced within 1-2 weeks of pretests and ceased 1-2 weeks before immediate posttests. After immediate posttests, the majority of children were available to be tested with follow-up tests after 4-6 weeks of no training. Results: Findings revealed that both TD and DLD groups benefited from the training to significantly improve their complementation and FB scores. The gains achieved during immediate posttests were moreover maintained 6-8 weeks after training ceased, as revealed by preserved levels of performance during follow-up posttests. Conclusion: This research thus suggests new avenues for therapeutic interventions for children with DLD, namely, the incorporation of a program directly training complements, which holds the promise of a double benefit, both for these structures and for Theory of Mind.