Stem cell imaging and tracking generate a significant impact on regenerative medicine. Among the other techniques, optical imaging methods have emerged as widely used, given their high sensitivity, temporal resolution, and relative accessibility over MRI and PET. Conjugated polymer nanoparticles (CPNs) have emerged as fluorescent probes and have started to stand out due to their high photostability, intense brightness, and flexible design possibilities. They have become promising tools for long-term stem-cell labeling and noninvasive monitoring due to their structural versatility, allowing adjustment of the emission properties and surface functionalities. This chapter provides a comprehensive overview of the role of CPNs in stem cell imaging, their structural and photophysical properties, strategies for cellular labeling, and performance within different optical imaging methods. The representative applications in monitoring migration, proliferation, and differentiation are highlighted, while challenges related to cytotoxicity, biodegradability, and reproducibility are discussed. Emerging approaches, including near-infrared (NIR-II) probes, multimodal systems, and stimuli-responsive designs, are addressed. By summarizing current progress and future directions, this chapter provides a comprehensive outlook on the potential of CPNs to advance next-generation tools for stem cell tracking and regenerative medicine.