Purpose: The aim of this study was to synthesize bevacizumab-loaded nanoparticles and evaluate their effects on the treatment of posterior segment diseases via subtenon injections. Methods: Bevacizumab-loaded chitosan nanoparticles (BLCNs) were synthesized by the ionic gelation method, and their physicochemical characteristics and in vitro release profile were studied. The BLCNs were characterized using atomic force microscopy (AFM), FTIR spectroscopy, dynamic light scattering, and scanning electron microscopy. The BLCNs were delivered into rabbits' eyes via posterior subtenon injections. An immunohistochemical evaluation of the ocular tissues was performed, and the vitreous humor and serum bevacizumab levels were measured by ELISA. Results: Bevacizumab-loaded chitosan nanoparticles with a diameter of 80 to 380 nm were prepared and characterized. In vitro studies showed that after the first 5 days of the experiment, a significant increase in the drug release maintained the desired drug dosage for 3 weeks. Immunohistochemical in vivo studies revealed that there were BLCNs penetrating through the sclera. Furthermore, the intravitreal bevacizumab concentration reached a maximum concentration of 18 μg/ml, and it decreased to 6 μg/ml after only a week. Conclusion: The results revealed that subtenon injection of BLCNs is a promising alternative to intravitreal injections. In addition to the ELISA studies, immunohistochemical experiments confirmed that BLCNs enable transscleral bevacizumab penetration, and BLCN usage may provide the required bevacizumab levels for the treatment of posterior segment diseases.