Cellulose, the most abundant organic polymer on Earth, has garnered significant interest across a myriad of scientific and industrial domains. The burgeoning utilization of cellulose nanocrystals (CNCs) has underscored the critical importance of understanding the interactions between CNCs and cellulose derivatives. Herein, the interactions between commercial cellulose ethers (METHOCEL™) and CNCs were investigated. The adsorption dynamics of 11 types of methylcellulose and hydroxypropyl methylcellulose were quantified in 2D on CNC films using quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR). Furthermore, dynamic light scattering, electrophoretic mobility, and isothermal titration calorimetry (ITC) were utilized to elucidate the thermodynamic details of the adsorption processes in 3D in suspension. All cellulose ethers irreversibly adsorbed to CNCs in 2D, with higher hydroxypropyl content and lower methoxy content led to more adsorption in a flattened polymer conformation; In 3D, higher molecular weight led to more adsorption in a globular polymer conformation. The interactions between common hydrocolloid polymers and nanocellulose are important for the design of formulated products such as emulsions, gels, foams, and films.