This study highlights, for the first time, the effect of Algerian nettle (Urtica dioïca L.) water extract against some phytopathogens bacteria. Results showed that water extract exhibited high level of total phenol content (261.7 ± 5.1 mg g−1 GAE) and a remarkable antioxidant activity (IC50 = 20.0 ± 0.6 µg mL−1) comparable to Trolox as reference (IC50 = 16.5 ± 0.5 µg mL−1). Moreover, results showed that water extract presented an interesting inhibition of some Gram-positive and Gram-negative phytopathogens’ bacteria. These results highlighted that secondary metabolites from Urtica dioïca could be an alternative pathway to synthetic pesticides for plant diseases control.