Plant natural products are low molecular weight compounds playing important roles in plant survival under biotic and abiotic stresses. In the rhizosphere, several groups of plant natural products function as semiochemicals that mediate the interactions of plants with other plants, animals and microorganisms. The knowledge on the biosynthesis and transport of these signaling molecules is increasing fast. This enables us to consider to optimize plant performance by changing the production of these signaling molecules or their exudation into the rhizosphere. Here we discuss recent advances in the understanding and metabolic engineering of these rhizosphere semiochemicals.