Plants have a variety of enzymes which help defend from pathogen attack by producing antimicrobial compounds. One of these enzymes,?agmatine?coumaroyl?transferase?(ACT) is responsible for producing hydroxycinnamic acid amides (HCAAs). In this study, we identified a tightly clustered group of?ACT?genes in?Brachypodium distachyon?responsive to?Fusarium?infection and functionally characterised one of these genes designated as?BdACT2a. It was found that when expression of?BdACT2a?is disrupted,?Brachypodium?becomes more susceptible to?Fusarium pseudograminearum. BdACT2a has broad?substrate specificity?and feruloylagmatine is produced in significantly lower quantities in the?Bdact2a?line compared to wild-type?Brachypodium. Feruloylagmatine appears to inhibit?spore germination?but not?mycelium?growth of Fusarium. This report demonstrates that BdACT2a is important for plant defence and ACTs may have a conserved defensive role in plants.