The brown planthopper (BPH), Nilaparvata lugens (St?l), is a serious insect pest on rice. It uses its stylet to collect rice sap by penetrating rice phloem, meanwhile it delivers saliva into the host plants to participate in the herbivore-plant interaction. The molecular mechanisms of BPH salivary proteins triggering plant responses are poorly understood. We screened transcriptomic data from different BPH tissues and found a salivary gland-specific protein NlG14 that could induce cell death in plants in the preliminary experiment. Here, we found that the NlG14 was uniquely found in the insect family Delphacidae. NlG14 was mainly localized in the A-follicle of principal gland (APG) of salivary gland, and was secreted into rice during feeding. Knockdown of NlG14 resulted in significant lethality when BPH was fed on either rice plant or artificial diet. Further analysis showed that NlG14 triggered reactive oxygen species (ROS) accumulation, cell death, callose deposition, and jasmonic acid (JA) signaling pathways in plants. Transient expression of NlG14 in Nicotiana benthamiana decreased insect feeding and suppressed plant pathogen infection. Thus, NlG14, an essential salivary protein of N. lugens, acted as a potential HAMP (herbivore-associated molecular pattern) to enhance plant resistance to both insects and plant pathogens by inducing multiple plant defense responses. Our findings provide a new insight into the molecular mechanisms of insect-plant interactions and offer a potential target for pest management.