Abstract Cellulose nanocrystals (CNCs) with amphiphilic features were used in oil drop stabilization in diesel oil-in-water (o/w) emulsion. The functionalized CNCs were synthesized from a lignin-rich reject cellulose source from the pulp and paper industry, i.e., the non-bleached fines fractions of carton pulp. Partial periodate-chlorite oxidation, which was followed by reductive butylamination, was used to obtain surface-modified amphiphilic CNCs. All studied CNCs prevented droplet coalescence by stabilizing oil droplets in the emulsion thus resulting in stable o/w Pickering-like emulsions. CNCs from the fines fractions at concentrations 0.05–0.1% (weight by weight, w/w) provided high stability against creaming (i.e., phase separation), and they did not de-emulsify at low temperatures since the oil droplet size remained small at + 5 °C at a 0.05% (w/w) CNC concentration. Salinity improved the stability against creaming with the reference chemical pulp CNC, but negatively affected the emulsion creaming rate for CNCs that had a higher level of lignin. However, the non-bleached fines fraction of the pulp may provide one potential and cost-effective raw material source for the development of a novel bio-based chemical.