Today cancer is one of the main causes of death all over the world. Chemotherapy, which is one of the main therapies in the treatment of cancer, causes several side effects by damaging healthy cells. Therefore, carbon nanomaterial systems have been developed to optimize therapeutics procedures with the least negative consequences. Targeting nanographene oxide (NGO) with folic acid (FA) molecules allows the recognition of MCF-7 cells, which are folic acid receptor (FR) positive. Harmine is a pharmacologically active secondary metabolite that is produced by Peganum harmala. It is found that this metabolite induces apoptosis to human breast cancer cell lines by intercalating DNA molecules. In this study, harmine was loaded on FA-NGO (FA-NGO/harmine) via π-π stacking and hydrophobic interactions and the cytotoxicity against MCF-7, as FR positive cancerous cell, and fibroblast cells, as normal FR negative cell, were investigated. The in vitro studies illustrated that FA-NGO/harmine have remarkably higher cytotoxicity against MCF-7 cells, about 60% cell loss, in comparison with free harmine with 40% cell loss (in the concentration of 40 μg. mL-1). However, the released amount of harmine into normal fibroblast cells was considerably low, only 28% cell loss in dose of 40 μg. mL-1. Our results suggest that the controlled release of harmine into FR positive cancerous cells might have a substantially high cytotoxicity effect.