Contextualization: Fusarium graminearum is a field microorganism that affects grasses and causes great losses, particularly to rice crops. To counter these phytosanitary problems, excessive amounts of pesticides are applied, causing damage to health and the environment. An alternative is to plant extracts with a high content of bioactive compounds.   Knowledge gap: The pyrogallol tannins contained in Caesalpinia spinosa pods have biological properties, Fusarium graminearum's micellial growth inhibition is effective at low concentrations of UFC/ml.   Purpose: Therefore, the objective in this research was to determinate in vitro the antifungal activity of tare phenolic compounds (Caesalpinia spinosa) against Fusarium graminearum.   Methodology: Firstly, the phenolic compounds extracted by maceration and heating (60 °C) through water and ethanol-water mix, the phenolic compounds content in the extracts determined by Folin-Ciocalteu method. Secondly, a Fusarium strain obtained from a rice culture isolated and identified by taxonomic keys, after cell suspensions made with concentrations 10⁷ and 10⁶ UFC/ml. For in vitro evaluation, a disc with an inoculum of each suspension placed in a culture medium containing C. spinosa extract.   Results and conclusions: Consequently, the aqueous extract by heating with a content of 5.88 g gallic acid/100 g dry sample inhibited 30 and 70% of mycelial growth of Fusarium graminearum with a concentration of 10⁷ and 10⁶ UFC/ml. Phenolic compounds of Caesalpinia spinosa have properties of interest for the control of Fusarium graminearum and can be tested in vivo, in the greenhouse.