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In this work, the antioxidant properties of methanolic extract of <i>Larrea tridentata</i> were assessed through the free radical scavenging method, ferric reducing antioxidant power and oxygen radical absorbance capacity. The phenolic acids content in the extract was quantified by high-performance liquid chromatography (HPLC) and the total phenol content by the Folin&#8722;Ciocalteu method. The extract was used as an antioxidant in biodiesel from canola oil composed mostly by fatty acid methyl esters identified and quantified by gas chromatography-mass spectrophotometry (GC-MS). The performance of the extract as an antioxidant was assessed by the oxidative stability index (OSI) with a Rancimat equipment at 100, 110, 120 and 130 &#176;C. Additionally, the change of the peroxide value (PV) and the higher heating value under conditions of oxidative stress at 100 &#176;C and air injection were measured. The antioxidant capacity of the extract reached 50,000 TAEC (micromole of Trolox antioxidant equivalent capacity per gram). The biodiesel was constituted by more than 70% of unsaturated fatty acid methyl esters (FAME), mainly methyl oleate. The time needed to reach a PV of 100 meqO₂/kg was almost four times longer with an antioxidant concentration of 250 mg/L than the blank. The biodiesel showed an OSI time of 1.25 h at 110 &#176;C, while it increased to 8.8, 15.89 and 32.27 h with the antioxidant at concentrations of 250, 500 and 1000 mg/L, respectively. The methanolic <i>Larrea tridentata</i> extract proved to have an antioxidant capacity and it is a green antioxidant in biodiesel to increase its oxidative stability. According to the results obtained, the <i>L. tridentata</i> methanolic extract is an alternative to the commercial synthetic antioxidants used in biodiesel nowadays.