Phthalides are important bioactive constituents of celery plants. The medicinal uses of celery and their characteristic aroma have been linked to the phthalides. In this report, the leaf and stalk oils of celery were extracted either by hydrodistillation or maceration in water and the phthalide constituents of the oils were characterized by gas chromatography-mass spectrometry (GC-MS) analysis. The leaf oil consists mainly of dihydroxyphthalides while the volatile phthalides are the main phthalides in the stalk oil. The phthalide content of the leaf oil and the stalk oil are 39.8% and 29.95% respectively. The phthalides identified in the leaf oil are the isomeric compounds of senkyunolide I and senkyunolides (J & N), while the major phthalide constituents of the stalk oil include 3-n- butylphthalide, sedanolide, neocnidilide and sedanenolide/senkyunolide A. The results suggest that the Nigerian celery plant could be considered a good source of phthalides which are known for their nutraceutical properties such as anti-oxidant, antitumor, anti- platelet aggregation, hypotensive, hypoglycemic and hypolipidemic properties. Further phytochemical and pharmacological evaluation of the locally cultivated celery are required in order to exploit the medicinal potentials of the plant for applications in pharmaceutical and cosmetic industries.