The current study first describes the chemical composition of the leaf essential oil of Cinnamomum subpenninervium Kosterm. ex H.H. Pham collected from Nghe An province, Central Vietnam. By the GC-FID/MS (gas chromatography-flame ionization detection/mass spectrophotometry) analysis, more than thirty compounds were identified, representing 99.92%. The obtained essential oil from the fresh leaves was dominated by non-terpenic compounds (57.07%), monoterpene hydrocarbons (23.03%) and oxygenated monoterpenes (13.34%), as well as E-cinnamaldehyde (38.56%), linalool (12.20%), benzyl benzoate (11.33%), and α-pinene (8.12%). C. subpenninervium showed strong antimicrobial activity against the fungus Fusarium oxysporum ATCC 46591 with the MIC (minimum inhibitory concentration) value of 64 µg/mL.