In this study, we evaluated the allelopathic effects of essential oils (EOs) from six different plant species, namely, lavender (), hyssop (), English thyme (), lovage (), costmary (), and cumin (), on seed germination and seedling growth of barley () and wheat (). The main constituents of the EOs of were 47.0% linalool acetate and 28.4% linalool; main constituents were 39.8% cis-pinocamphone, 9.8% trans-pinocamphone, 11.4% β-pinene, and 7.5% β-phellandrene; were 38.2% para-cymene, 25.6% thymol, and 13.6% γ-terpinene; were 64.8% α-terpinyl acetate and 14.7% β-phellandrene; 's were 43.7% camphor, 32.4% trans-thujone, and 11.6% camphene; were 49.6% cumin aldehyde, 10.4% para-cymene, 11.6% α-terpinen-7-al, and 9.1% β-pinene. All six EOs exhibited an allelopathic effect and suppressed the seed germination and seedling development of wheat and barley; however, the concentrations that exhibited a suppressing effect were different among the plants. EO completely suppressed both barley and wheat germination at 10-, 30-, and 90-µL application rates, making it the most effective treatment among the tested EOs. and EOs at 30 and 90 µL application rates completely suppressed barley and wheat radicles per seed, radicle length (mm), seedling height (mm), and germination (%). EOs at 30- and 90-µL and EO at 90 µL application rates also completely suppressed barley and wheat radicles per seed, radicle length (mm), seedling height (mm), and germination (%). , , , and EOs at a 10 µL application rate reduced barley radicle length, seedling height, and % germination relative to the control. Wheat seed germination % was completely suppressed by the application of and EOs at 30 and 90 µL, while EO at 10 µL rate reduced the germination relative to the control. Interestingly, and at 10 µL did not reduce wheat germination; however, they did reduce the number of radicles per seed, radicle length (mm), seedling height (mm), germination (%), and vigor index. Furthermore, EO reduced the measured indices (radicles per seed, radicle length, seedling height, and vigor index) at the 10, 30, and 90 µL application rates relative to the non-treated control; however, none of the application rates of EO had a suppression effect on wheat germination. This study demonstrated the allelopathic effects of the EOs of six different herbal plant species on seed germination of barley and winter wheat. The results can be utilized in the development of commercial products for controlling pre-harvest sprouting of wheat and barley. Further research is needed to verify the results under field conditions.