<p><strong>Abstract</strong><strong>: </strong>The damage of chilli, an important spice fruit, comes from fungal diseases caused mainly by <em>Aspergillus niger</em> and <em>Colletotrichum</em> sp. The fungi on chilli fruits would directly harm consumers’ health. Plant extracts containing bio-active compounds with antimicrobial properties could be a good possible solution to deal with the fungi. This study aims to evaluate the <em>in vitro</em> and <em>in vivo</em> efficacy of aqueous extracts from the leaves of <em>Ageratum</em> plants against <em>A. niger</em> and <em>Colletotrichum</em> sp. The results show that the optimal efficacy of the treatment of <em>Ageratum</em> leaf extract is at a concentration of 6%, with the efficacy of <em>Ageratum</em> leaf extract<strong> </strong>on colonial diameter at approximately 43–44% for the two fungi at 96 hours after inoculation. The 6% <em>Ageratum</em> leaf extract has a high efficacy (~54.23%) on limiting the development of <em>Aspergillus</em> rot lesions on chilli fruits 4 days after inoculation. Meanwhile, the efficacy of the extract on <em>Colletotrichum</em> lesions is 11.34%, lower than that of <em>Aspergillus</em> rot.</p><p><strong>Keywords:</strong><strong> </strong><em>Ageratum</em><em> </em>leaf<em> </em>extract,<strong> </strong>chilli fruit,<em> </em>rot lesion</p>