An individual’s decision to pursue a career in the public sector is likely to be influenced by a combination of intrinsic and extrinsic factors. While the widely studied concept of Public Service Motivation (PSM) emphasizes altruistic and prosocial values, it does not fully capture the diverse motivations that may influence entry into, and performance within the public sector—particularly in developing country contexts where economic constraints, political dynamics, and cultural hierarchies are prominent. The present study addresses this limitation by conceptualizing and validating a novel instrument to measure Public Sector Motivation (PSecM) which encompasses both intrinsic and extrinsic dimensions of motivation specific to a public sector employment. Through three studies involving diverse samples from the Indian civil services, this research conceptualizes PSecM as a construct having three key dimensions: power to bring change, job security, and social respect, thereby highlighting that PSecM in India is driven by mixed motives, combining intrinsic aspirations for societal impact and extrinsic incentives tied to the unique characteristics of public sector jobs. Next, through a sequence of rigorous psychometric analysis, the study presents a valid measure of PSecM scale that has adequate psychometric properties as well as predictive validity. By providing a conceptual understanding of PSecM and developing a valid instrument to measure it, this study contributes to the broader discourse on public sector management and national development in resource-constrained environments.