The paper presents a conceptual framework and a metric instrument for assisting design and evaluating serious games for dementia family carers as the first step towards designing a game specifically designed to cater for their needs. The paper starts with a literature survey on dementia, dementia family carers and existing games for health issues. From this survey, three components of the carers’ needs (health, education and social), three platforms (social marketing, social media and games) and six game contents (game play, avatar portrayal, game world graphics, sound / music and storyline) were identified, and engagement as the metric of interaction was also identified. With these, a conceptual framework was constructed, identifying the relationship amongst these elements. Based on these, the metric instrument is devised using the Goal Question Metric (GQM) method. An exploratory experiment was conducted with six health-related games and five game professionals to assess the effectiveness of the instrument. It is found that the instrument can identify the successfulness of the games in terms of satisfying the three categories of needs of the carer, i.e., health, education and social, though it was suggested that a further experiment with more participants and focusing on one game would be needed to further verify the effectiveness of the instrument.