This study was conducted between the years of 2017-2018 to determine the effect of rosemary (Rosmarinus officinalis L.) of which its allelochemical effect is known, on the germination of some weeds such as; redroot pigweed (Amaranthus retroflexus L.), lamb's quarters (Chenopodium album L.), black nightshade (Solanum nigrum L.), and corn (Zea mays L.) and sugar beet (Beta vulgaris L.). In the study, the methanol, aqueous extracts (15, 20, 25 %), essential oil (9, 18, 36 4/Petri dishes) and hydrosol (4, 8, 10 %) of the rosemary was used. It was determined that the seed germinations of all test plants were inhibited in significant amounts depending on the increase of concentration in all applications performed. The highest effect was obtained from the methanol extracts and it was determined they had that inhibited the germination of seeds of C. album and B. vulgaris at a ratio of 96 %. According to the results obtained, it is considered that the plant of rosemary to have herbicide effect will contribute to the use and development of biopreparations, which are sensitive to the human health and environment; and in addition, to the pest control of integrated weeds.