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As important transcription factors, WRKYs play a vital role in the defense response of plants against the invasion of multiple pathogens. Though some WRKY members have been reported to participate in pepper immunity in response to <i>Ralstonia solanacearum</i> infection, the functions of the majority of WRKY members are still unknown. Herein, <i>CaWRKY22b</i> was cloned from the pepper genome and its function against <i>R. solanacearum</i> was analyzed. The transcript abundance of <i>CaWRKY22b</i> was significantly increased in response to the infection of <i>R. solanacearum</i> and the application of exogenous methyl jasmonate (MeJA). Subcellular localization assay in the leaves of <i>Nicotiana benthamiana</i> showed that CaWRKY22b protein was targeted to the nuclei. <i>Agrobacterium</i>-mediated transient expression in pepper leaves indicated that <i>CaWRKY22b</i> overexpression triggered intensive hypersensitive response-like cell death, H₂O₂ accumulation, and the up-regulation of defense- and JA-responsive genes, including <i>CaHIR1</i>, <i>CaPO2</i>, <i>CaBPR1</i>, and <i>CaDEF1</i>. Virus-induced gene silencing assay revealed that knock-down of <i>CaWRKY22b</i> attenuated pepper’s resistance against <i>R. solanacearum</i> and the up-regulation of the tested defense- and jasmonic acid (JA)-responsive genes. We further assessed the role of CaWRKY22b in modulating the expression of JA-responsive <i>CaDEF1</i>, and the result demonstrated that CaWRKY22b trans-activated <i>CaDEF1</i> expression by directly binding to its upstream promoter. Collectively, our results suggest that CaWRKY22b positively regulated pepper immunity against <i>R. solanacearum</i> in a manner associated with JA signaling, probably by modulating the expression of JA-responsive <i>CaDEF1</i>.