Essential oil formulation of Thymus capitatus L. (wild and cultivated thyme) and Majorana hortensis L. (marjoram) were investigated for allelopathic activity against Convolvulus arvensis and Setaria viridis seeds and seedling growth. Thymol, camphor, carvacrol, thujone, ä-terpinene, borneol, p-cymene, carvacrol, 1,8-cineole, caryophyllene oxide, á-humulene á-pinene, borneol, â-pinene, caryophyllene, caryophyllene oxide, linalol and phellandrene were detected by GC-Ms analysis from the oil contents. Macroemulsion (Mac-E) and nanoemulsion (Nano-E) were formulated from oil by adding co-surfactant and surfactant. These formulations were subjected to stability stresses and were tested for herbicidal activity against C. arvensis seeds germination and seedling growth. Nanoemulsion had particle size of 5.3, 12.0 and 22.1 nm for M. hortensis, T. capitatus wild and T. capitatus cultivated, respectively. Depending on ED50 M. hortensis (oils, Mac-E and Nano-E) exhibited strong allelopathic activity on C. arvensis, however, the lowest activity was achieved from T. capitatus cultivated followed by T. capitatus wild. The Nano-E exhibited pronounced post-emergence properties on (5-7 leaves stage) than others formulation on C. arvensis in greenhouse conditions.