Electrosterically stabilized nanocrystals of cellulose (ENCCs) have emerged recently as new cellulose nanoparticles among common nanocrystals of cellulose (NCCs) and cellulose nanofibers. ENCC has a special structure being composed of a crystal with protruded amorphous chains at each endcaps bearing carboxyl groups. Here, we studied the intrinsic viscosity of aqueous suspensions of ENCCs as a function of pH and ionic strength. Low pH or high ionic strength reduced the ENCCs to rigid rod-like particles while a polyelectrolyte-like behavior was observed for suspensions of ENCCs around pH 7 and at low ionic strength. The pH had a great effect on charges due to both deprotonation of carboxyl groups and counter-ion effect, while the ionic strength only affected the surface charges of the particles. The zeta potential of ENCC suspensions was measured as a function of pH and ionic strength to establish a link between particle charges and the intrinsic viscosity. Finally, the Fedors model was used to compare our data in the case of rigid rod-like body behavior with literature data on NCC suspensions and the model was shown to be unsuitable.