The bacteriocin production by Lactic acid bacteria (LAB) isolated from soil, dairy products, was studied using the culture medium (MRS). The bacteriocin produced by LAB inhibits the Ralstonia solanacearum strains. Bacterial wilt caused by R. solanacearum is one of the production constraints of tomato. The aim of the study is to evaluate the potential of bacteriocin from Lactobacillus paracasei subsp. tolerans to suppress the development of wilt pathogen in tomato. R. solanacearum was isolated from infected tomato plants on triphenyl tetrazolium chloride (TZC) medium. The antibacterial compound from the culture supernatant was found to be proteinaceous in nature and it identified as bacteriocin. The bacteriocin from Lactobacillus paracasei subsp. tolerans was found to be heat–stable (121ºC for 15 min) and active over a wide pH range of 4.0–10.0. It showed stability (60%) for 30 days at room temperature (30–32 ºC). Addition of surfactants up to 1% to crude bacteriocin showed increase in antibacterial activity where as metal ions in low concentration (0.5–1mg/l) decreased the activity. Seed treatment with bacteriocin significantly improved the quality of seed germination and seedling vigour. The disease incidence was significantly reduced by about 63 % in plants raised from seed treatment and soil drench method. The present work demonstrates for the first time the ability of bacteriocin to act as plant growth promoting and biocontrol agent against R. solanacearum invivo.