Background <p>Healthy living behaviours play a central role in preventing chronic disease and improving population health; therefore, understanding the quality of motivation behind these behaviours is essential. This study aimed to explore the motivational factors that shape the adoption and maintenance of healthy living behaviours within the framework of Self-Determination Theory.</p> Methods <p>A qualitative phenomenological design was employed. Semi-structured interviews were conducted with 18 adults living in different regions of Türkiye who had experience with healthy living. Data were analyzed using thematic analysis.</p> Results <p>Motivation for healthy living was found to be multidimensional and emerged from the interplay of intrinsic and extrinsic factors. Participants reported that concerns related to aging and health, physical and psychological well-being, social desirability, family and social support, illness experiences, and cultural and spiritual values influenced their motivation. Some factors reflected intrinsic motivation, whereas several external influences were internalised over time and became more autonomous. Satisfaction of autonomy, competence, and relatedness needs played a central role in the sustained practice of healthy living behaviours.</p> Conclusions <p>Motivation for healthy living is shaped not only by individual benefits but also by social, cultural, and spiritual contexts. The findings offer new insight into the process of motivational internalization and may guide public health strategies aimed at strengthening individuals’ motivational resources.</p> Trial registration <p>Not applicable. This study was not a clinical trial.</p>