Phenolic compounds of tigernut tubers were extracted by methanol, colorimetrically determined, separated and identified using HPLC. Also, antioxidative assay of this extract was tested using DPPHradical scavenging activity method. Furthermore, these extracts were tested as antioxidants for corn oil compared to BHA. Also, these extracts were tested as antimicrobial agent against some microbial strains. The results showed that total phenolic compounds recorded about 197.20 mg/100g and the methanolic yield was 1.02%. ρ-hydroxy benzoic acid was the major phenolic compound (54.95 mg/100g) followed by salicylic acid (37.41 mg/100g); then cholchecien (35.25 mg/100g). Antioxidative activity of tiger nut phenolic extract was lower than that of BHA at all used concentrations. Phenolic extract at all used concentrations had lower antioxidative activity (indicated by peroxide, thiobarbituric acid and acid values) compared to BHA in corn oil. Antimicrobial test reflected that this extract had antimicrobial activity against gram (-) and (+) but lower than phenol 1%, as well as against Saccharomyces spp., and only against Aspergillus niger at 50% concentration.