The escalating environmental and health concerns associated with synthetic chemical fungicides necessitate the urgent exploration of sustainable, natural alternatives for enhancing human and animal health. This study investigated the bioactive potential of Acalypha marginata, a plant species with a history of use in folk medicine for various ailments. The primary objective was to analyze its phytochemical profile and evaluate its leaf extracts' antioxidant and in vitro antifungal activities against significant pathogenic fungi. To achieve this, we systematically examined the impact of different extraction methods (ultrasound-assisted, heat-assisted, and conventional) and various solvent systems (distilled water, 50 %, 80 %, and 100 % acetone, ethanol, and methanol in water) on the extraction yield and bioactivity of A. marginata leaf extracts. Our findings revealed that an 80 % methanol solution coupled with ultrasound-assisted extraction (UAE) for 1 h was the most efficient method, resulting in a high extract yield of 23.09 ± 0.036 %. This optimal extract exhibited a notable total anthocyanin content of 15.27 ± 0.058 mg CGE/g DWE and a substantial total phenolic content of 493.5 ± 3.775 mg GAE/g DWE. Furthermore, it demonstrated significant antioxidant capacity with an IC50 value of 6.680 ± 0.003 μg/mL, surpassing the activity of L-ascorbic acid by 3.5-fold. The same extract also displayed superior in vitro antifungal activity, achieving 100 % inhibition against the mycelial growth of Alternaria alternata and Sclerotinia sclerotiorum, and varying levels of inhibition against Fusarium proliferatum. The phytochemical analysis using liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS/MS) led to the unambiguous identification of 38 phenolic compounds, a novel finding for this species. Rutin was identified as the major constituent in the 80 % methanol extract and subsequently confirmed to possess significant antifungal activity. Principal component analysis (PCA) further corroborated the positive correlation between extraction methods, solvent selection, phenolic content, antioxidant, and antifungal activities. This research provides the first insight into the phytochemical composition of A. marginata leaves and its promising antioxidant and antifungal properties, strongly advocating for the 80 % methanol extract obtained via UAE as a valuable resource for developing eco-friendly fungicides against and exploring its potential as a source of natural antioxidants for food and health applications.