Summary The biocontrol agent P ythium oligandrum and its elicitin‐like proteins oligandrins have been shown to induce disease resistance in a range of plants. In the present study, the ability of two oligandrins, Oli‐D1 and Oli‐D2 , to induce an immune response and the possible molecular mechanism regulating the defence responses in N icotiana benthamiana and tomato were investigated. Infiltration of recombinant Oli‐D1 and Oli‐D2 proteins induced a typical immune response in N . benthamiana including the induction of a hypersensitive response ( HR ), accumulation of reactive oxygen species and production of autofluorescence. Agrobacterium ‐mediated transient expression assays revealed that full‐length Oli‐D1 and Oli‐D2 were required for full HR ‐inducing activity in N . benthamiana , and virus‐induced gene silencing‐mediated knockdown of some of the signalling regulatory genes demonstrated that NbSGT1 and NbNPR1 were required for Oli‐D1 and Oli‐D2 to induce HR in N . benthamiana . Subcellular localization analyses indicated that both Oli‐D1 and Oli‐D2 were targeted to the plasma membrane of N . benthamiana . When infiltrated or transiently expressed in leaves, Oli‐D1 and Oli‐D2 induced resistance against B otrytis cinerea in tomato and activated the expression of a set of genes involved in the jasmonic acid/ethylene ( JA / ET )‐mediated signalling pathway. Our results demonstrate that Oli‐D1 and Oli‐D2 are effective elicitors capable of inducing immune responses in plants, probably through the JA / ET ‐mediated signalling pathway, and that both Oli‐D1 and Oli‐D2 have potential for the development of bioactive formulae for crop disease control in practice.