Tolerance to fusarium root rot caused by Fusarium oxysporum f. sp. asparagi (Foa, MAFF305556 and N9-31) and the changes in antioxidative abilities in mycorrhizal asparagus (Asparagus officinalis L., cv. Welcome) plants were investigated. Asparagus plants were inoculated with arbuscular mycorrhizal fungus (AMF, Glomus sp. R10) and Foa was inoculated 10 weeks after AMF inoculation. AMF plants accumulated higher dry weight of ferns and roots than non-AMF plants before and after Foa inoculation. AMF colonization level reached more than 70% and no difference noted among the treatments. As for disease tolerance, non-AMF plants showed 100% in incidence of root rot and highest severity in both Foa isolates; the severity of symptom was relatively higher in MAFF305556 compared with N9-31. However, AMF plants showed lower severity than non-AMF plants in both Foa isolates. Before and after Foa inoculation, antioxidative abilities increased in most of the AMF plants than non-AMF in the following items: activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and total contents of polyphenol and ascorbic acids. These results suggest that plant growth enhancement and tolerance to fusarium root rot appeared in mycorrhizal asparagus plants. In this case, the disease tolerance might be associated with the increase in antioxidative ability.