Background: The evolving complexity of the medical field in developing countries, driven by operational realities and changing patient expectations, creates unique challenges and opportunities. Exploring the theoretical mechanisms and effect of job satisfaction as a mediator, on doctors’ in-role performance and professional intentions, is essential for enhancing healthcare outcomes and retaining skilled professionals. Methods: Cross-sectional correlational design was employed, using structural equation modelling to test the hypothesized model. Data from 2120 doctors were analysed using statistical methods including Matrix Correlation, Exploratory Factor Analysis, and Confirmation Factor Analysis. Python-based data visualization and analysis techniques were also used to explore relationships between variables. Results: In Nigeria, intrinsic factors collectively have a significant positive impact on job satisfaction, whereas in China, this is true only individually. Extrinsic factors significantly influence job satisfaction in both countries. There is a strong relationship between job satisfaction, in-role performance, and professional intentions in both countries. This indicates that job satisfaction not only enhances doctors’ current job performance but also positively affects their future career intentions and commitment to the profession. Both Nigeria and China show similar patterns in ranking career fulfilment drivers, with an intrinsic factor followed by five major extrinsic factors and another intrinsic factor, reflecting shared perceptions in both countries. Conclusion: The dynamics between intrinsic and extrinsic motivators suggest that while both are essential, their relative importance may vary based on external conditions such as economic stability and healthcare infrastructure. Therefore, strategies aimed at improving in-role performance and retention should be multifaceted and context specific.