Achieving sustainable health solutions requires interdisciplinary methodologies that integrate psychological research with public health strategies. While biomedical science provides critical advancements, it often overlooks the behavioral, social, and psychological factors that influence health outcomes. This chapter explores four key psychology-rooted methodologies—Community-Based Participatory Research (CBPR), Stakeholder Engagement Models, Citizen Science, and Patient Involvement in Research—which enhance inclusivity, equity, and long-term effectiveness in global health interventions. By embedding behavioral science into health research, these methodologies ensure that interventions are scientifically rigorous, culturally attuned, and responsive to real-world needs. CBPR fosters co-creation and community ownership of health initiatives, while stakeholder engagement models align diverse interests for collaborative decision-making. Citizen science democratizes health research by involving non-scientists in data collection and advocacy, and patient involvement frameworks, such as PROMs (Patient-Reported Outcome Measures) and PREMs (Patient-Reported Experience Measures), strengthen patient-centered innovation by integrating lived experiences into research and care. This chapter underscores the necessity of bridging psychological insights with traditional scientific paradigms to recover the human factor in global health. As health challenges grow increasingly complex, the integration of participatory and behavioral methodologies is essential for creating adaptive, equitable, and sustainable healthcare systems that truly reflect the needs of the populations they serve.