Disease suppression of Fusarium crown rot and the changes in free amino acid contents in mycorrhizal asparagus (Asparagus officinalis L., cv. “Welcome”) plants were investigated. Sixteen weeks after arbuscular mycorrhizal fungus (AMF; Glomus intraradices) inoculation, mycorrhizal plants showed higher dry weight of shoots than non-mycorrhizal plants, and AMF colonization level in a root system reached up to 73.3%. Ten weeks after Fusarium proliferatum (Fp; N1-31, SUF1207) inoculation, control plants showed 100% incidence and high severity in the 2 Fp isolates. However, AMF plants showed lower severity than non-AMF plants in the 2 Fp isolates. Ten weeks after Fp (N1-31) inoculation, the increase in 7 constituents of amino acids (glutamine, arginine, aspartic acid, alanine, citrulline, GABA, glycine) in shoots, and 9 in roots (asparagine, arginine, threonine, serine, glutamine, citrulline, valine, GABA, histidine) occurred in AMF plants. From these findings, plant growth promotion and suppression of Fusarium crown rot occurred in mycorrhizal asparagus plants, and the disease tolerance was supposed to be associated with the symbiosis-specific increase in free amino acids.