Worldwide, the growing number of senior citizens is a major source of concern in many countries. Recent developments in digitally mediated games aim to encourage exercise among users. It is generally reported in the well-established Technology Acceptance Model (TAM) that users' positive perceptions of ease of use and usefulness with IT systems will be sufficient to predict users' behavioural intention to use the systems. This paper describes a study to explore effects of digitally-mediated exercises such as those in Nintendo Wii on elderly users. We first developed a theoretical model based on TAM linking the antecedents into the key factors using information acquired from an extended literature review. We then undertook a survey of thirty elderly participants at a senior citizens centre in Singapore. Data collection was carried out via a self-reported questionnaire and video observation. Through the use of statistical tests, our findings showed that perceived ease of use and perceived health value were determinants of perceived usefulness. Perceived affective response mediates the influence of perceived usefulness on satisfaction, leading to elderly users' behavioural intention to use. The paper concludes with a discussion on the design and impact of digitally mediated games for elderly users.