Red pigments of a newly discovered fungus, Gelatinomyces siamensis recently characterized and classified in Leotiomycetes, Incertae Sedis were produced in liquid media. The role of this apparent reddish color was questioning. Therefore, the red pigments produced by the fungus were extracted with ethyl acetate and butanol to obtain two fractions of crude substances to seek for biological activities. The results suggested crude extract derived from ethyl acetate was significantly greater in antioxidation and total phenolic compounds compared with the extract due to butanol. Additionally, both crudes were screened for other biological assays. While the butanol fraction was inactive in all tests, the ethyl acetate fraction was active against phytopathogenic fungus, Magnaporthe grisea with minimal inhibitory concentration (MIC) of 50.00 µg/ml and against cancer cells (NCI-H187-Small cell lung cancer) with half maximal inhibitory concentration (IC₅₀) of 20.44 µg/ml. This could provide supports to further investigate the pigment derived from ethyl acetate extraction. Moreover, preliminary identification of chemical components were performed using gas chromatography mass spectrometry (GCMS) implying the compounds contained in both fractions were mainly acids and components associated with pigment producing pathways.