Nano-sized and well-dispersed chitosan particles (CSPs) are prepared by adjusting pH towards pKa of chitosan (CS) aqueous solutions. The prepared CSPs are able to stabilize high internal phase Pickering emulsions (HIPPEs) with low CSP contents, at minimum of 0.2 wt% CSP stabilizing a maximum of 85 % oil phase fraction in a near-neutral environment. It is clarified by microscopy, small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) measurements that CSPs act as Pickering particle emulsifiers to form a network immobilizing oil droplets in HIPPEs. Using power-law analysis on SAOS results, the solid-like but frequency-dependent rheological response is attributed to the physical connection among CSPs, while the overshoot of the loss modulus in LAOS test is assigned to the featured resistance of networks to the applied large deformation. The oil phase fraction, CSP concentration, temperature and ionic strength are found to be key factors for the rheological behavior and emulsion stability. This work is expected to guide the design and processing of HIPPE stabilized solely by polysaccharides.