Background: Mung bean is susceptible to Rhizoctonia solani infection. Applications of beneficial microorganisms such as Trichoderma are promising for controlling pathogens and promoting plant growth. Methods: This study investigated growth performance and metabolic changes in mung bean seedlings during interaction with R. solani and Trichoderma virens using Gas Chromatography-Mass Spectrometry (GC-MS). Result: Mung bean infected by R. solani caused root rot and wilting. T. virens treatment reduced the disease severity in infected seedlings and promoted mung bean growth. Seventy-eight metabolites were identified in root extracts and dominated by sugars and fatty acids. The sugars, fatty acids and organic acids were significant metabolite groups that changed in response to pathogen infection and/or T. virens treatment. Five metabolic pathways particularly pyruvate metabolism, glyoxylate and dicarboxylate metabolism, sulfur metabolism, citrate cycle (TCA cycle) and phenylalanine, tyrosine and tryptophan biosynthesis altered significantly based on a metabolic pathway analysis. Acetic acid and aconitine had important roles in mung bean response to R. solani infection and/or T. virens treatment.