Folic acid (FA) is used as a recognition molecule to achieve selective internalization in cancer cells. Here functionalized gold nanoparticles with folic acid (AuNP-FA) are proposed as suitable therapeutic agents for cervix cancer cells by photothermal damage. The functionalized gold nanoparticles with folic acid were synthesized by mixing hydrogen tetrachloroaurate with folic acid in a molar ratio of 0.56/1 under radiation of mercury lamp (λmax=254 nm). HeLa cells were incubated with AuNP-FA during 48 h, then were irradiated and the cytotoxicity was analyzed 12 h after irradiation. The AuNP-FA were dose-dependent cytotoxic under irradiation and not cytotoxic in the absence of radiation. The viability of cancer cells treated with functionalized and non-functionalized gold nanoparticles (AuNPs), with and without near infrared light at 808 nm, was measured by MTT assays. This work provides useful guidance toward the synthesis of biocompatible nanomaterials for biological applications.