Cellulose nanomaterials (CNMs), such as cellulose nanocrystals (CNCs), are expected to play a major role in the current environmental and societal transition towards a larger use of bio-based products. They demonstrate a great potential as sustainable and high-performance fillers for the development of materials with tunable rheological, thermo-mechanical, optical and barrier properties. Currently they are mainly used in paper manufacturing, packaging, membranes and bioengineering. As other nanoparticles, the dispersion of CNMs in thermoplastic polymers remain a huge challenge for the development of polymer nanocomposites. Several approaches have been studied to improve their dispersion and the mechanical properties of the nanocomposites, by using solvent and melt based processes with various thermoplastic polymers as well as physico-chemical and processing aids. In this work, a comparative study is made of these different processes applied to polyvinyl alcohol (PVA)/CNC formulations, starting from “classical” processes, such as melt extrusion and solvent casting, to more innovative ones, such as wet compounding. The impact of the processing route on the dispersion of CNCs in PVA is discussed, in particular through rheological analyses performed on PVA/CNC suspensions and molten PVA/CNC composites.