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The essential oil derived from <i>Citrus</i> plants has long been used for medicinal purposes, due to its broad spectrum of therapeutic characteristics. To date, approximately 162 <i>Citrus</i> species have been identified, and many investigational studies have been conducted to explore the pharmacological potential of <i>Citrus</i> spp. oils. This study investigated the volatile constituents of essential oil distilled from the leaves of <i>C. hystrix</i>, <i>C. limon</i>, <i>C. pyriformis</i>, and <i>C. microcarpa</i>, using gas chromatography–quadrupole mass spectrometry. A total of 80 secondary compounds were tentatively identified, representing 84.88–97.99% of the total ion count and mainly comprising monoterpene (5.20–76.15%) and sesquiterpene (1.36–27.14%) hydrocarbons, oxygenated monoterpenes (3.91–89.52%) and sesquiterpenes (0.21–38.87%), and other minor chemical classes (0.10–0.52%). In particular, 27 compounds (1.19–39.06%) were detected across all <i>Citrus</i> species. Principal component analysis of the identified phytoconstituents and their relative quantities enabled differentiation of the <i>Citrus</i> leaf oils according to their species, with the loading variables contributing to these metabolic differences being identified. The <i>Citrus</i> leaf oils were tested for their antioxidant and antiproliferative activities using 2,2-diphenyl-1-picryl-hydrazylhydrate (DPPH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. The results indicated that <i>C. limon</i> displayed the highest DPPH radical scavenging ability (IC₅₀ value of 29.14 ± 1.97 mg/mL), while <i>C. hystrix</i> exhibited the lowest activity (IC₅₀ value of 279.03 ± 10.37 mg/mL). On the other hand, all the <i>Citrus</i> oils exhibit potent antiproliferative activities against the HeLa cervical cancer cell line, with IC₅₀ values of 11.66 μg/mL (<i>C. limon</i>), 20.41 μg/mL (<i>C. microcarpa</i>), 25.91 μg/mL (C. <i>hystrix</i>), and 87.17 μg/mL (C. <i>pyriformis</i>).