The protein nanocarrier system provides various benefits, including successfully delivering loaded drugs into cancer cells. The present work successfully developed corosolic acid-encapsulated kafirin nanoparticles (CA-Kaf NPs) to deliver corosolic acid (CA) into MCF-7 cells. The hydrophobic character of CA fails to reach the disease site. Initially, kafirin protein was isolated from sorghum grains and characterized. Then, CA was loaded into kafirin protein using a modified desolvation method, and their physicochemical properties, stability, drug release, and cytotoxic potential were investigated. The efficiency of encapsulating corosolic acid into Kaf NPs was 81.13 ± 1.27% (w/w), and the loading capacity was 8.38 ± 0.51% (w/w). The CA-Kaf NPs exhibited an amorphous nature and spherical shape with a size range of 300-400 nm and a zeta potential of +2 mV. CA-Kaf NPs release CA slowly and steadily in an acidic medium (pH 5.4), and the CA release rate was significantly higher at pH 5.4 (75.17±0.06% (w/w)) compared to pH 7.2 (73.02±0.22% (w/w)). CA-Kaf NPs significantly reduced the viability of MCF-7 cells after 24 h with an IC50 value of 58.08 μg × mL−1 and induced apoptosis. MCF-7 cells treated with CA-Kaf NPs showed standard apoptotic morphological changes, including contracted nuclei and damaged membrane bodies. The release of corosolic acid from CA-Kaf NPs significantly increases reactive oxygen species and damages the integrity of the mitochondrial membrane potential. These findings imply that CA-Kaf NPs, which target the delivery of corosolic acid into MCF-7 cells and facilitate endocytosis, could have a significant therapeutic potential for breast cancer.