Calamansi (Citrus macrocarpa), a citrus fruit widely used in the Philippines, produces substantial peel waste, particularly in Northern Luzon, where it is a key condiment in Filipino stir-fried noodles commonly known as “pansit”. Despite the nutritional and culinary importance of calamansi, its peels, which are rich in essential oils, remain underutilized. This study aims to profile the chemical composition of calamansi peel essential oil extracted using a fabricated extractor machine for community use and to evaluate its antimicrobial properties. Gas Chromatography-Mass Spectrometry (GC-MS) identified 109 compounds in the extracted oil, with D-limonene comprising 65.59%. The antimicrobial activity was tested against various bacterial and fungal strains using the disc diffusion method. The oil showed partially active to very active inhibitory effects against Staphylococcus aureus, Staphylococcus pyogenes, and Bacillus subtilis, particularly at higher concentrations (up to 10%). Additionally, it demonstrated significant antifungal activity against Aspergillus flavus, Aspergillus niger, and Aspergillus fumigatus, with the 10% concentration yielding comparable results to positive control. These findings highlight the potential of calamansi peel essential oil as a natural antimicrobial agent with applications in food preservation, pharmaceuticals, and cosmetics. The study also emphasizes the economic and environmental benefits of repurposing calamansi peel waste, suggesting that future research may focus on optimizing extraction methods and exploring higher concentrations for enhanced efficacy. published by the Journal of Biodiversity and Environmental Sciences (JBES)