BACKGROUND Phenylboronic acid (PBA) is an environmentally non‐toxic substance with antimicrobial activity. Due to increasing ecological limitations in phytopharmacy and considering the development of resistance of phytopathogenic bacteria to available antibacterial agents, here we explore a possible role of PBA as an antibacterial agent of choice. RESULTS We determined a minimal inhibitory concentration (MIC) of PBA in vitro on the Pseudomonas syringae pv. tomato (Pst) (0.5 mg/mL) and Erwinia amylovora (0.8 mg/mL), two of the most damaging plant pathogenic bacteria. In comparison, boric acid MIC was 2.5–6‐fold higher than that of PBA, indicating enhanced antibacterial efficacy of the latter. Moreover, we determined the effect of PBA on cell growth and viability of both bacteria and have shown that PBA has bactericidal effect in concentrations > 1.0 mg/mL, whereas in lower concentration it is bacteriostatic. In addition, we have shown that PBA impairs Pst ability to cause symptoms on tomato plants in a dose‐dependent manner, whereas solely applied PBA did not affect plant morphology at bactericidal concentrations. CONCLUSION We report, for the first time, that PBA is a suitable agent for controlling phytopathogenic bacteria. PBA has bacteriostatic activity in lower, and bactericidal activity in higher (> 1.0 mg/mL) concentrations. When applied on tomato plants, PBA managed to suppress symptoms caused by Pst, while having no adverse effect on plants at the bactericidal concentrations. As an additional benefit, PBA is environmentally friendly. © 2022 Society of Chemical Industry. Increasing ecological limitations in phytopharmacy and development of phytopathogenic bacteria resistance to available antibacterial agents, makes finding new agents extremely important. Here, phenylboronic acid had pronounced antibacterial activity against common phytopathogenic bacteria Pseudomonas syringae and Erwinia amylovora in both in vitro and in vivo assays, with no adverse impact on test tomato plants.