Costus spiralis (Costaceae) is a species native to the Amazon region and is used in traditional medicine. The endophytic fungi used in this study were obtained from leaves of this plant. 13 strains were selected to obtain hydroethanolic extracts and were submitted to hydroalcoholic extraction and evaluated for antioxidant activity by DPPH (2,2-difenil-1-picrilhidrazil) and FRAP (ferric reducing antioxidant power), and all of the fungi had positive results. The antimicrobial action of crude extracts had a good range of activities. All extracts had inhibitory activities against the yeasts of Candida albicans and C. parapsilosis, with 125 to 500 μg/mL MIC. Eight extracts had antimicrobial activities against Bacillus subtilis (MIC from 62.4 to 125 μg/mL), 5 against Pseudomonas aeruginosa (MIC from 125 to 500 μg/mL), 2 against Salmonella enterica (MIC from 125 to 62.5 μg/mL), and 2 against Enterococcus faecalis (MIC from 500 to 125 μg/mL). The presence of secondary metabolites, including coumarins, was observed during chemical evaluation by thin layer chromatography. Total phenol content was estimated, and a strong positive correlation to antioxidant activity was observed, according to its Pearson coefficient. This is the first report of the bioactive potential of endophytic fungi isolated from the Costaceae family in Brazilian ecosystems.