The emergence of wearable activity trackers (WATs) has transformed the way individuals monitor and manage their health and fitness. Over the past decade, these devices have gained immense popularity among young adults, particularly millennials, who are known for their embracement of technology and their pursuit of a healthier lifestyle. However, there is a lack of research examining the usage, interaction patterns, and overall motivation of millennials with activity trackers, especially in the Indian context. This study aims to explore the motivations of Indian millennials with WATs through the lens of Self-Determination Theory (SDT), a widely recognized theoretical framework that emphasizes the importance of intrinsic and extrinsic motivational factors in shaping human behavior. Employing a qualitative approach, we conducted in-depth semi-structured interviews with a diverse sample of Indian millennials (n = 10) experienced in using WATs. The findings suggest that the adoption and continued use of these devices are influenced by a complex range of factors, including the fulfillment of autonomy, competence, and relatedness needs, alongside extrinsic influences, as delineated in SDT. These insights can inform the design and development of more effective and engaging wearable technology solutions.