The abuse of synthetic pesticides in weed management causes serious environmental problems: disruption of ecological balance, harmful effects on human health and higher incidence of herbicide-resistant weeds. Due to this, efforts are being directed to develop new eco-friendly compounds with non-toxic effects and new modes of action. Some plant secondary metabolites are an important source to formulate new bioherbicides. Monoterpenes are one of the largest and most important groups of secondary metabolites, some of which have an already reported phytotoxic activity that makes them interesting as potential bioherbicides. This paper summarizes the proved effects of individual monoterpenes and their mode of action on plant-plant interactions.