The necrotrophic phytopathogen causes leaf spot and root rot in tobacco, which significantly reduce the yield and quality of the crop. Recently, much attention has been paid to effectors, but only a few of them have been characterized. Here, we identified a CAP domain-containing protein, RsCAP3, with a functional signal peptide, which triggers slight cell death on tobacco leaves. Meanwhile, RsCAP3 dramatically induces salicylic acid (SA) signaling but inhibits jasmonic acid (JA) signaling, increasing the plant's susceptibility to . Moreover, we demonstrated that RsCAP3 interacts with Nb14-3-3b, a negative regulator of tobacco resistance to . Correspondingly, we also found that transient expression of activates SA signaling while suppressing JA signaling. Based on these results, we propose that RsCAP3 hijacks Nb14-3-3b to disrupt JA and SA pathways, thereby facilitating the infection of . Our findings highlight a novel virulence strategy in which interferes with the JA-/SA-mediated defense response.