Abstract—: Among natural chemopreventive agents, polyphenol curcumin and naphthoquinone juglone, which has broad-spectrum anticancer activity, are highly valued. Fatty acid-binding proteins (FABPs), which vary depending on the type of cancer, are small (14–15 kDa) proteins belonging to the lipid-binding protein superfamily. FABPs are located in many tissues and play an essential role in fatty acid metabolism, cell growth, and proliferation. It is suggested that they can be used as tumor markers. The objective of this work is to study the effects of curcumin and juglone on cell viability and to evaluate their anticancer and cytotoxic effects and changes in the FABP5 and FABP9 gene expression and protein levels in breast cancer cell lines MCF-7 and MDA-MB-231. Information on FABP5 and FABP9 gene expression in BRCA (breast invasive cancer) and normal cells was collected from the GEPIA2 and UALCAN databases. MTT analysis revealed that the IC50 (concentration of half maximal inhibitory effect) in MCF-7 cells was 22.4 and 16.3 μM for curcumin and juglone, respectively, and in MDA-MB-231 cells, 10.4 and 3.4 μM for curcumin and juglone, respectively. In both cell lines, FABP5 and FABP9 gene expression and protein levels were also analyzed. We found that treatment of MCF-7 cells with curcumin and juglone reduced cell viability, expression of the FABP5 and FABP9 genes, and the levels of the FABP5 and FABP9 proteins. In the MDA-MB-231 cell line, the FABP5 and FABP9 levels were increased at low doses of curcumin and juglone and decreased at higher doses.