β-Carbonic anhydrase (βCA) is very important for plant growth and development, but its function in immunity has also been examined. In this study, we found that the expression level ofSolanum lycopersicum βCA1(SlβCA1) was significantly upregulated in plants treated withXanthomonas euvesicatoria85-10. The protein was localized in the nucleus, cell membrane and chloroplast. Using tomato plants silenced withSlβCA1, we demonstrated that SlβCA1 plays an active role in plant disease resistance. Moreover, we found that the elicitor PopW upregulated the expression ofSlβCA1, while the microbe-associated molecular pattern response induced by PopW was inhibited in TRV-SlβCA1. The interaction between PopW and SlβCA1 was confirmed. Here, we found that SlβCA1 was positively regulated during PopW-induced resistance toXanthomonas euvesicatoria85-10. These data indicate the importance of SlβCA1 in plant basic immunity and its recognition by the Harpin protein PopW as a new target for elicitor recognition.