Geraniol is a dietary monoterpene alcohol that is found in the essential oils of aromatic plants. To date, experimental evidence supports the therapeutic or preventive effects of geraniol on different types of cancer, such as breast, lung, colon, prostate, pancreatic, and hepatic cancer, and has revealed the mechanistic basis for its pharmacological actions. In addition, geraniol sensitizes tumor cells to commonly used chemotherapy agents. Geraniol controls a variety of signaling molecules and pathways that represent tumor hallmarks; these actions of geraniol constrain the ability of tumor cells to acquire adaptive resistance against anticancer drugs. It has been shown that geraniol inhibits HMG-CoA reductase in most types of tumor cells, which raises the possibility that the reduced prenylation of small G-proteins, such as Ras or RhoA, accounts for the antitumor effects of geraniol. In addition to its use in various commercial products, including cosmetics and fine fragrances, geraniol exerts a broad spectrum of pharmacological activities, such as anti-microbial, anti-inflammatory, anti-oxidant, anti-ulcer and neuroprotective activities. Geraniol is classified into the generally recognized-as-safe (GRAS) category by the Flavor and Extract Manufacturers Association (FEMA) and the Food and Drug Administration (FDA) of the United States.