The aim of the present study was to investigate the essential oil composition of Monarda didyma L. during different phenological stages i.e. pre flowering, full flowering and seed setting. Hydrodistilled essential oils obtained from the aerial parts of the plant were analyzed by GC and GC/MS. Total twenty compounds were identified in the oils representing 98.53%, 98.13% and 97.19%, respectively in pre flowering, full flowering and seed setting stages. In all the oils collected at different phenological stages, linalool was found as the major constituent which ranged from 47.12-61.89% followed by γ-terpinene (15.20-24.11%), thymol methyl ether (4.35-9.53%), p-cymene (2.28-6.09%), thymol (3.09-5.15%) and 1-octen-3-ol (1.75-3.75%). The maximum content of linalool (61.89%) was found at pre-flowering stage, γ-terpenene (24.11%) at flowering and thymol methyl ether (9.53%) at seed setting stages. All the oils were dominated by oxygenated monoterpenes (60.83-75.54%) followed by monoterpenes hydrocarbons (19.92-35.83%), while sesquiterpene hydrocarbons ranged from only 1.47-3.07%. The study concluded that however the oils were qualitatively similar but differed quantitatively during different growth stages.