The present study was undertaken to investigate antifungal activity and GC-MS analysis of n-butanol fraction of methanolic leaf extract of Chenopodium mural L. Dried leaves of C. murale were extracted with methanol for 2 weeks. After evaporating the solvent on a rotary evaporator, the remaining extract was fractioned using various organic solvents. n-Butanol fraction was assayed for antifungal activity against Fusarium oxysporum f. sp. lycopersici, isolated from diseased tomato roots. Different concentrations of the extract ranging from 1.562 to 200 mg mL^-1, reduced fungal biomass significantly over control. A 100 mg mL^-1 concentration almost completely controlled fungal growth and reduced its biomass by 98% over control. The extract was subjected to GC-MS analysis that revealed presence of 34 compounds. The predominant compounds in the extract were 1-heptanol (10.01%), 3-hydroxyhexanoic acid (9.70%), n-methyldodecylamine (6.63%), decane (6.54%), 1,2-decanediol (5.50%) and 1-octanol (4.71%).