Calcium carbonate nanoparticles have salient properties, such as biocompatibility, pH responsiveness, and the ability to alkalinize a tumor, hence reducing metastasis. A combination therapy regimen is normative for breast cancer, where, besides its side effects, toxic vehicles are required for certain drugs. This study is aimed at transforming the readily available Blood cockle shells (Anadara granosa) to calcium carbonate nanoparticles (CSCaCO₃NP), loading them with Gefitinib (GEF) and Paclitaxel (PTXL). Facile top-down synthesis of CSCaCO₃NP is comprised of grinding, sieving, and stirring with Tween 80, followed by filtration and finally dry milling for 100 hours. A ratio of 1+0.5:25 of GEF+PTXL: CSCaCO₃NP in an equal admixture of DMSO and 0.05%Tween 80 buffer was used for drug loading. Loading content (%) and encapsulation efficiency (%) for GEF and PTXL in dual drug-loaded NP (GEF-PTXL-CSCaCO₃NP) was 1.98 ± 0.11, 50.01 ± 2.18 and 0.92 ± 0.01, 45.60 ± 0.32. Field emission Scanning electron micrographs revealed that the nanoparticles were almost spherical with the average diameter (nm) measuring 63.96 ± 22.3 and 87.20 ± 26.66 for CSCaCO₃NP and GEF-PTXL-CSCaCO₃NP. The Dynamic Light Scattering data gives the average diameter of CSCaCO₃NP and GEF-PTXL-CSCaCO₃NP as 179 ± 10.9 (nm) and 274 ± 23.22 (nm), respectively, and polydispersive index of 0.3. Zeta potential was -17 ± 1.15 (mV) and 10.30 ± 1.7 (mV), respectively. Fourier-transform Infrared spectroscopy proves that CSCaCO₃NP has encapsulated the drugs. X-Ray Diffraction data indicates that the aragonite phase is unaltered. N₂ adsorption-desorption isotherms reveal that CSCaCO₃NP are mesoporous and that the surface area had reduced from 10.68 ± 0.22 to 9.88 ± 0.24 m²/g after drug loading. For the first time, this work will describe the process to synthesize CSCaCO₃NP which was used as a carrier to load GEF and PTXL and its salient characteristics.