Due to the limitations and side effects of current treatment methods, targeted drug delivery systems using chemotherapeutics in the treatment of breast cancer have been widely investigated in recent years. The synthesis, characterization and biocompatibility studies of the cancer drug lapatinib (LAP) encapsulated in zeolitic imidazolate framework-8 (ZIF-8), one of the metal organic frameworks (MOF), were carried out and its cytotoxic effects were revealed in two different cancer cell lines. LAP encapsulated into ZIF-8 (LAP@ZIF-8) was synthesized with encapsulation efficiency of 72.42% and drug loading of 6.55%. Various characterization analyzes were used and evaluated to determine the particle size and images of LAP@ZIF-8, its hydrodynamic diameter, zeta potential, chemical content, functional groups/chemical bonds, crystallinity/structure, and finally its thermal properties. The release ability at pH 5.5 compared to pH 7.4 showed the controlled release of the drug in the acidic tumor microenvironment. While the serum protein binding study result showed that LAP@ZIF-8 was biocompatible, the hemolysis experiment showed that it was hemocompatible, harmless to fresh blood, and could be used in biologically practical applications. The IC50 value of LAP@ZIF-8 in SKBR-3 cell line was 9.38, 3.81, and 1.20 μg/mL after 24 h, 48 h, and 72 h incubation time, respectively. The IC50 value of LAP@ZIF-8 in MCF-7 cell line was 22.05, 16.13, and 9.14 μg/mL after 24 h, 48 h, and 72 h incubation time, respectively. The developed LAP@ZIF-8 nanoparticle system is thought to have the potential to achieve optimal therapeutic effect for use in breast cancer treatment