In spite of various researches on Haplophyllum A. Juss. species essential oils, there was no report on Haplophyllum laeviusculum C. C. Towns. (Rutaceae) and in this article volatile components of this Iranian endemic species is informed for the first time. The essential oil obtained by hydrodistillation from flowering aerial parts of Haplophyllum laeviusculum C. C. Towns. was analyzed using gas chromatography (GC) and gas chromatography– mass spectrometry (GC–MS). Thirty six constituents constituting 95.7% of the total oil were detected. The major ingredients were β-Pinene (20.1%), α-Phellandrene (11.7%), β-Caryophyllene (7.6%), Myrcene (6.8%), Linalool (6.1%) and Limonene (5.6%). The volatile oil of Haplophyllum laeviusculum C. C. Towns. flowering aerial parts was characterized by high amounts of monoterpene hydrocarbons (56.3%).