This study reported methylene blue (MB) dye decolorization by using mixed consortium culture, brown-rot fungus (BRF) Gloeophyllum trabeum which is known as degradative fungus with bacterium Bacillus subtilis addition. B. subtilis were added into G. trabeum cultures at variation 2, 4, 6, 8, and 10 mL and incubated statically (1 mL = 9.47 × 108 CFU). All of mixed cultures had ability to decolorize MB (100 mg/L) in potato dextrose broth (PDB) medium during incubation process at 30 °C for 7 days. The addition of 10 mL B. subtilis in fungus culture showed the highest of MB decolorized, approximately 82%, while using G. trabeum culture only was approximately 11%. The metabolites of MB biodecolorization were identified and characterized by LC-TOF/MS, which were N-(7-(dimethylamino)-1-hydroxy-3H-phenothiazin-3-ylidene)-N-methylmethanaminium; 2-amino-5-(dimethylamino)-3-((3-(dimethylamino) phenyl) sulfinyl) phenol; and N-7-(7-(dimethylamino)-1,4,6,9-tetrahydroxy-3H-phenothiazin-3-ylidene)-N-methylmethanaminium. Those results could indicate that the mixed consortium culture of BRF G. trabeum with B. subtilis addition were efficient for dye wastewater treatment.