With this study, we tried to understand how the adaptation of a manipulative material can facilitate the learning of the decomposition of natural numbers in a child with Down Syndrome. Many authors defend the use of manipulative materials to teach Mathematics to children with Down Syndrome and, also, recommend the Cuisenaire material to promote the learning of mathematical initiation concepts. However, we found that the child we study presents difficulties in terms of fine manipulation and abstraction. We promoted the adaptation of the Cuisenaire material to this student and developed an intervention program of twenty sessions, divided into three phases: manipulation of the adapted Cuisenaire; manipulation of conventional Cuisenaire and the performance of exercises. In all sessions, the child worked on the decomposition of natural numbers and the exploration of the train game. After analyzing the data collected, we found that the dimensions and textures of the adapted Cuisenaire allowed us to overcome some of the difficulties felt in terms of manipulation and abstraction and facilitated the learning of decomposing natural numbers to ten. However, the adapted Cuisenaire did not facilitate the manipulation of the conventional Cuisenaire.