Allelopathic effect of Aloe vera (L.) Burm.f. on seed germination and seedlings growth of seven plant species was investigated. The experiment was conducted out in Petri dishes and extracts from fresh leaves of A. vera at various concentrations (2, 4, 6, 8, and 10%) were evaluated on germination, seedlings length and fresh and dry weight of seedlings of barley, wheat, soybean, oil pumpkin, radicchio, rocket and lettuce. The effect of water extracts depended on the extract concentration and test species. Extract with concentrations above 2% reduced germination of barley and lettuce seeds, while positive effect was observed on oil pumpkin. The highest decrease of root length was recorded for lettuce by 41.6%, while the root length of oil pumpkin was increased up to 49.9%. Water extracts significantly increased shoot length of wheat, soybean and oil pumpkin. Both positive and negative effects were observed on the fresh weight of test species seedlings, while the dry weight of seedlings was reduced only for barley in all treatments, and for lettuce in the treatment with extract concentration of 4%. Among the test species barley proved to be the most sensitive in all measured parameters, except in root length.