An investigation was carried out on the effect of spent mushroom substrateon the wilt disease of tomato when the spent substrate is used as soilamendment. The experiment was carried out at the teaching and researchFarm of the Faculty of Agriculture and the Mycology/Plant Pathology Laboratoryof the Department of Plant Science and Biotechnology, University ofPort Harcourt. Two tomato varieties tropimech (TT 3) and tomate U82B(TT2)at 4 Ã¢â‚¬Â6wks old stage were transplanted into potted soil amended with spentmushroom substrate at the ratio 1:3, 1:4, 1:5 and 1:6 in plastic pots. Stemdiameter, plant height, number of leaves, disease incidence and disease severitywere evaluated. Fusarium oxysporum was implicated as the causalagent of the disease; Aspergillus sp and Rhizopus sp were also isolated fromthe soil though not pathogenic to the plants. The ratio 1:4 was observed tohave the most positive effect on the disease, while the ratio 1:5 had the leasteffect on the disease.