People generally want to engage in a healthy lifestyle, to live in harmony with the environment, to contribute to social causes, and to avoid behaviours that are harmful for themselves and others. However, people often find it difficult to motivate themselves to engage in these beneficial behaviours. Even adopting a healthy lifestyle, such as healthy eating, physical activity, or smoking cessation, is hard despite being aware of the benefits. The increasing adoption and integration of technologies into our daily lives present unique opportunities to assist individuals to adopt healthy behaviours using technology. As a result, research on how to use technology to motivate health behaviour change has attracted the attention of both researchers and health practitioners. Technology designed for the purpose of bringing about desirable behaviour and attitude changes is referred to as Persuasive Technology (PT). Over the past decade, several PTs have been developed to motivate healthy behaviour, including helping people with addictive behaviour such as substance abuse, assisting individuals to achieve personal wellness, helping people manage diseases, and engaging people in preventive behaviours. Most of these PTs take a one-size-fits-all design approach. However, people differ in their motivation and beliefs about health and what constitutes a healthy life. A technology that motivates one type of person to change her behaviour may actually deter behaviour change for another type of person. As a result, existing PTs that are based on the one-size-fits-all approach may not be effective for promoting healthy behaviour change for most people. Because of the motivational pull that games offer, many PTs deliver their intervention in the form of games. This type of game-based PTs are referred to as persuasive games. Considering the increasing interest in delivering PT as a game, this dissertation uses persuasive games as a case study to illustrate the danger of applying the one-size-fits-all approach, the value and importance of tailoring PT, and to propose an approach for tailoring PTs to increase their efficacy. To address the problem that most existing PTs employ the one-size-fits-all design approach, I developed the Model-driven Persuasive Technology (MPT) design approach for tailoring PTs to various user types. The MPT is based on studying and modelling user’s behaviour with respect to their motivations. I developed the MPT approach in two preliminary studies (N = 221, N = 554) that model the determinants of healthy eating for people from different cultures, of different ages, and of both genders. I then applied the MPT approach in two large-scale studies to develop models for tailoring persuasive games to various gamer types. In the first study (N = 642), I examine eating behaviours and associated determinants, using the Health Belief Model. Using data from the study, I modelled the determinants of healthy eating behaviour for various gamer types. In the second study (N = 1108), I examined the persuasiveness of PT design strategies and developed models for tailoring the strategies to various gamer types. Behavioural determinants and PT design strategies are the two fundamental building blocks that drive PT interventions. The models revealed that some strategies were more effective for particular gamer types, thus, providing guidelines for tailoring persuasive games to various gamer types. To show the feasibility of the MPT design approach, I applied the model to design and develop two versions of a Model-driven Persuasive Game (MPG) targeting two distinct gamer types. To demonstrate the importance of tailoring persuasive games using the MPG approach, I conducted a large-scale evaluation (N = 802) of the two versions of the game and compared the efficacy of the tailored, contra-tailored, and the one-size-fits-all persuasive games condition with respect to their ability to promote positive changes in attitude, self-efficacy, and intention. To also demonstrate that the tailored MPG games inspire better play experience than the one-size-fits-all and the contra-tailored persuasive games, I measure the gamers’ perceived enjoyment and competence under the different game conditions. The results of the evaluation showed that while PTs can be effective for promoting healthy behaviour in terms of attitude, self-efficacy, and intention, the effectiveness of persuasion depends on using the right choice of persuasive strategy for each gamer type. The results showed that one size does not fit all and answered my overarching research question of whether there is a value in tailoring PT to an individual or group. The answer is that persuasive health interventions are more effective if they are tailored to the user types under consideration and that not tailoring PTs could be detrimental to behaviour change.