Wall-associated kinases (Waks) are important components of plant immunity against various pathogens, including the bacterium <i>Pseudomonas syringae</i> pv. tomato (Pst). However, the molecular mechanisms of their role(s) in plant immunity are largely unknown. In tomato (<i>Solanum lycopersicum</i>), wall-associated kinase 1 (SlWak1), has been implicated in pattern recognition receptor (PRR)-triggered immunity (PTI) because its transcript abundance increases significantly after treatment with the flagellin-derived, microbe-associated molecular patterns flg22 and flgII-28, which activate the PRRs Fls2 and Fls3, respectively. We generated two <i>SlWak1</i> tomato mutants (Δwak1) using CRISPR/Cas9 gene editing technology and investigated the role of <i>SlWak1</i> in tomato–<i>Pst</i> interactions. Late PTI responses activated in the apoplast by flg22 or flgII-28 were compromised in Δwak1 plants, but PTI at the leaf surface was unaffected. The Δwak1 plants developed fewer callose deposits than wild-type plants, but retained early PTI responses such as generation of reactive oxygen species and activation of mitogen-activated protein kinases upon exposure to flg22 and flgII-28. Induction of Wak1 gene expression by flg22 and flgII-28 was greatly reduced in a tomato mutant lacking Fls2 and Fls3, but induction of Fls3 gene expression by flgII-28 was unaffected in Δwak1 plants. After Pst inoculation, Δwak1 plants developed disease symptoms more slowly than Δfls2.1/2.2/3 mutant plants, although ultimately, both plants were similarly susceptible. SlWak1 coimmunoprecipitated with both Fls2 and Fls3, independently of flg22/flgII-28 or of BRASSINOSTEROID INSENSITIVE1-ASSOCIATED RECEPTOR KINASE1. These observations suggest that SlWak1 acts in a complex with Fls2/Fls3 and is important at later stages of PTI in the apoplast.Los datos de secuencia de este artículo se pueden encontrar en Plant Genome Editing Database (http://plantcrispr.org) como Solyc09g014720Instituto de Fisiología Vegetal