This study aims at the investigation of using magnetic water (MW) to manage brown rot (bacterial wilt) disease of potato. The effect of magnetic field (MF) on the viability of Ralstonia solanacearum (the bacterial causal pathogen of this disease) was investigated by passing the suspension of R. solanacearum through a magnetic liquid modifier tube. The viable count of the bacterial pathogen increased with the increasing of the incubation time (1, 2, 3 and 4 h) as well as with increasing the number of passes through the magnetic tube. In the pots experiment (carried out at Tag El-Ezz Agricultural Research Station, Dakahlia Governorate, Egypt - during the period of 17 February to 12 May 2016), the irrigation with MW led to significant increases in total phenols, polyphenol oxidase, peroxidase, total chlorophylls, chlorophyll a chlorophyll b, and carotenoids. Significant increase in plant height after 50 and 70 days of planting and decrease in disease rating were noticed. The viable count of R. solanacearum in rhizosphere of the plant irrigated with MW was significantly decreased after 70 and 108 days of planting when compared with the plants irrigated with tap water (TW). The irrigation with MW led to significant increase in potato yield (25.64 %) and a significant decrease in the percentage of infected tubers (40.22 %) in comparing with the plants irrigated with TW. These studies encourage more studies for the use of MW to manage brown rot disease of potato as well as other plant diseases.