This study aims to evaluate antioxidant and antifungal activities from medicinal plant’ methanol extract, chitosan oligomer, and the two combined. Their antioxidative activity was spectroscopically assessed through 2,2-diphenyl-2- picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging assays. Alternatively, antifungal activity was determined through Phytophthora capsici's mycelial growth inhibition. DPPH and ABTS radical scavenging activities were observed at 1000 ppm concentrations for Glycyrrhiza uralensis extract (GU, 81.4%, IC50=238.4ppm; 83.5%, 199.5ppm, respectively), chitosan oligomer (ChiO, 64.8%, 438.2ppm; 66.6%, 314.5ppm), and GU+ChiO (78.3%, 329.7 ppm; 75.2%, 254.0 ppm). As the standard, ascorbic acid IC50 values were 112.0 and 101.7 ppm, respectively. GU, ChiO, and GU+ChiO at 2.5, 5.0, and 10.0 mg/mL concentrations significantly reduced Phytophthora capsici mycelial growth compared with the control treatment. GU+ChiO EC50 values were 2.04, 2.45, and 2.38 mg/mL at 3, 6, and 9 days after treatment, respectively. These results suggest that the GU and ChiO combination worked as elicitors, triggering enhanced P. capsici suppression in vitro.