Galium tunetanum Poiret (G. tunetanum) was extracted with different solvents (methanol, hexane, chloroform and ethyl acetate). Total phenolic and flavonoid contents of the extracts were estimated. The extracts were assayed for their antioxidant activities using six in vitro models (the 1,1-diphenyl-2 picrylhydrazyl (DPPH), ABTS, reducing power, ferrous chelating test, ß- carotene/ linoleic acid assay system, ferric thiocyanate method and thiobarbituric acid method). Methanol extract (ME) showed the highest polyphenolic content: 131.29 ± 0.501 mg gallic acid equivalent/g of dry extract. The determination of flavonoid contents showed that ethyl acetate extract (EAE) had the highest content of flavonoids: 96.93 ± 1.2 mg quercetin equivalent / g of dry extract. ME extract exhibited the most significant antioxidant activity on DPPH radical and ABTS with IC50 value of 0.02 ± 0.00023 mg/mL and 0.012 ±0.0015 mg/mL, respectively. Using the reducing power test, ME extract showed the highest scavenging activity with an EC50 of 0.19±0.01 mg/mL. Similarly, ME extract exerted the highest chelating activity towards ferrous ions with an IC50 value of 21 ± 0.002 mg/mL. ME and CHE inhibited the oxidation of ß- carotene in important level compared to BHT as positive reference. In addition, all fractions inhibited strongly the lipid peroxidation. In conclusion, the results show that G. tunetanum Poiret represents a source of antioxidant compounds.