Effective communication requires an understanding of the interlocutor's perspective. Being able to infer someone else's knowledge about a situation is a critical skill in any communication and social interaction. These abilities are part of Theory of Mind (ToM) skills and are known to be impaired in Down syndrome (DS). It therefore makes sense to investigate ToM development in this population. In our pilot study, we explore the possibility of improving ToM abilities in participants with DS and typically developing (TD) children matched for nonverbal mental age. Participants were assessed with the French adaptation of the "ToM Inventory" before and after a 10-week training session. Results show that trained groups perform significantly better on ToM tasks than untrained groups, whose performances remain stable between pre- and post-test. These results are encouraging as they suggest that, with a specific training, children with DS can improve their ToM skills.