Serious Games offer a new way to older adults to improve various abilities such as the vision, the balance or the memory. However, cognitive impairment causes a lot of difficulties to them when actively practicing these games. Their engagement and motivation are reduced rapidly when encountering successive problems without any help. In this paper, we present an approach to assist older adults in Serious Game using an interactive system. Three groups of players with different cognitive impairments (Mnesic Plaint, MCI and Alzheimer) have been tested with the system in a concentration-based game. As the experimental results, the players performed a high performance when playing with the assistance of the system, especially among Alzheimer group. The future work aims to perform this approach with a larger population and explore other factors which can influence on the players' motivation.