Astaxanthin is a strong antioxidant with numerous medicinal properties. However, it is highly lipophilic and has low bioavailability which hinders its absorption capabilities. In order to improve the absorption of astaxanthin, the present study evaluates the physicochemical characteristics of astaxanthin-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles prepared via the nanoprecipitation technique. An optimum formulation of nanoparticles was then tested for particle size, zeta potential, encapsulation and entrapment efficiency, morphology, thermal behavior, crystallinity, and compound-polymer interaction. The size of the particles and zeta potential of the formed nanoparticle were reported at 142.23 ± 0.961 nm and −27.3 ± 4.67 mV, respectively. Scanning electron microscope (SEM) study through photomicrogram confirmed the nano-range size of the optimum formulation. The formulation shows low nanoparticle yield but recorded high encapsulation efficiency. Density scanning calorimetry and X-ray diffraction results proved that the nanoparticles were in an amorphous state. Fourier transform infrared spectroscopy analysis had shown that the stretching vibrations of ketone and hydroxyl functional groups were restricted, indicating that the astaxanthin was encapsulated inside the PLGA polymer. These findings provide valuable information regarding astaxanthin bioavailability enhancement through the nanoprecipitation technique.