The development of innovative cosmetic ingredients has driven growing interest in emulsion systems that combine performance, stability, and sustainability. Pickering emulsions can form physically stable systems by adsorbing solid particles at the oil–water interface. In this study, bacterial cellulose nanofibers (CNFs) and nanocrystals (CNCs), obtained via acid hydrolysis, were evaluated as stabilizing agents in Pickering emulsions containing jojoba, castor, and grape seed oils for hair conditioning applications. Structural and physicochemical characterization revealed that CNCs exhibited higher crystallinity, a narrower size distribution, and a higher negative surface charge than CNFs, resulting in enhanced colloidal stability. Emulsion analyses showed that CNCs more effectively reduced interfacial tension and produced smaller, more homogeneous droplets. Stability assessments under pH variation, thermal stress, and storage demonstrated that CNC-stabilized emulsions, particularly with castor oil, maintained stability indices above 95% for up to 60 days, whereas CNF-based systems showed greater sensitivity to environmental conditions. The incorporation of CNCs into a prototype conditioning cream resulted in a creamy texture and improved physical stability without compromising formulation performance. Overall, these results highlight CNCs as robust and efficient stabilizing materials for Pickering emulsions, reinforcing the potential of bacterial nanocellulose in advanced cosmetic formulations.