Research in health promotion and illness prevention is essential for enhancing public health outcomes. It offers a foundation for understanding the complex factors that influence health behaviors and supports the creation of effective interventions. Health promotion emphasizes empowering individuals and communities to make healthier choices and improve their well-being, while illness prevention focuses on minimizing the occurrence of diseases and conditions through proactive strategies. Different research approaches are used to study health promotion and illness prevention. Qualitative methods, such as interviews and focus groups, offer insights into people’s experiences and perceptions, enabling researchers to explore social and cultural factors influencing health. Quantitative methods, like epidemiological studies and randomized controlled trials (RCTs), assess the effectiveness of interventions and identify patterns in health behaviors. A mixed-methods approach, which integrates both qualitative and quantitative research, is often employed to provide a deeper understanding of the complexities surrounding health behaviors. Familiarity with these research methods is crucial for creating strategies that not only address current health issues but also foster long-term changes that encourage healthier lifestyles and prevent illness on a larger scale. This chapter explores various research approaches commonly used in studies related to health promotion and illness prevention. It begins by examining the concepts of ontology and epistemology in research, followed by a discussion on the characteristics of qualitative, quantitative, and mixed-methods research. The chapter concludes by analyzing how these approaches are applied in the context of health promotion and illness prevention research.