Polystyrene microspheres are widely used in biomedical applications due to their uniform size and surface properties. They serve as effective carriers in drug delivery systems, enabling controlled release and targeted therapy. In diagnostics, they are used as standards in calibration of flow cytometers and particle counters, ensuring instrument accuracy. Their ability to be surface-functionalized makes them suitable for immunoassays and bioseparation techniques, such as cell isolation using magnetic coatings.

In research, polystyrene microspheres act as model particles for studying colloidal behavior, sedimentation, and aggregation processes. They are also employed in microscopy as tracers to visualize fluid flow and diffusion in microfluidic devices. In industrial applications, they are used as spacers in electronic materials, additives in coatings for texture and finish control, and in quality control for filter testing. Their optical properties make them useful in display technologies and as light-diffusing agents.