The cellulose nanocrystals (CNCs) are shown to interact with amine-functionalized polyhedral oligomeric silsesquioxane (POSS-NH2) strongly at the water/oil interface, forming the CNC-POSS assemblies, that is, CNC surfactants that decrease the interfacial tension of the water/chloroform greatly. When bringing the CNC aqueous solution and POSS chloroform solution into a Langmuir trough, they form a monolayer of the CNC surfactants. Upon applying a continuous compression, a distinct transition appears in the surface pressure-area curves, and during this transition, the packing of the CNC surfactants in the produced monolayers transits from network-like patterns to ordered alignment.