Starch nanocrystals (SNCs) have emerged as promising biodegradable nanomaterial for the enhancement of biopolymer films' properties. Nevertheless, using SNCs alone is difficult due to restricted capacity for nanocrystal integration within the film's matrix. The objective of this study was to enhance the properties of biopolymer films using waxy corn starch nanocrystals supplemented with stearic acid. Cassava starch films containing varying proportions of SNCs (0–20 wt.% starch) and steric acid (2%) were prepared and characterised. The inclusion of stearic acid substantially improved SNC integration from 5% to 15%, yielding nanocomposite films with better tensile strength, thermal stability and barrier properties than those prepared with native starch or starch‐fatty acid alone. The improvement in film properties was attributed to V‐amylose complexes formation, increased crystallinity and hydrophobicity. Microscopy images revealed homogenous film surfaces, depicting greater nanocrystal dispersibility. The supplementation of lipid additives offers a valuable strategy to improve the integration of SNCs in film matrices.