In this study, (2,‍2,‍6,‍6-tetramethylpiperidin-1-yl)oxyl-mediated (TEMPO-mediated) oxidized cellulose nanofibrils (TOCNFs) modified with octenyl succinic anhydride (OSA) to improve their hydrophobicity and emulsification performance were investigated. OSA loadings of 9.87-14.81 mmol/g (base on oven-dry weight of TOCNFs) were explored during modification, and the obtained OSA-modified TOCNFs (TOCNF-OSA) were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and thermogravimetric analysis. Additionally, the emulsification performance of TOCNF-OSA was also investigated in the preparation of the Pickering emulsion. The results demonstrated that the molecular chain of OSA was successfully grafted onto the backbone of TOCNFs during modification. With an increase in OSA loading, the content of the carboxyl group of the modified TOCNF-OSA increased significantly while the Zeta potential decreased. Moreover, a degree of substitution of 0.95 could be achieved at an OSA loading of 14.81 mmol/g. During the preparation of Pickering emulsions, compared with original TOCNFs, the modified TOCNF-OSA significantly improved the stability and dispersibility of the Pickering emulsion. This study demonstrated a promising approach for the modification of the Pickering emulsion to produce an eco-friendly emulsifier with superior performance for use in the food industry.