The purpose of this study was to examine the allelopathic effect of sweet marjoram (O. majorana) on the germination and early stages of maize seedlings. Two experiments were performed under laboratory conditions (in Petri dishes). In the first experience, Origanum majorana seeds were cogerminated with maize (Zea mays) seeds in the same Petri dish. For the second experience were used aqueous extracts from fresh and dry aboveground biomass of the sweet marjoram (stem, leaves) in concentrations of 1%, 2% and 3%. Cogermination of O. majorana with maize seeds has significantly stimulated the germination index (Gi) and growth of maize seedlings. Aqueous extracts of sweet marjoram in a concentration of 1% and 2% have significantly stimulated shoot length of maize. On the other hand, aqueous extracts at a concentration of 3% significantly inhibited root length of maize. These results suggest that the cogermination with sweet marjoram seeds may be an alternative to biostimulation of maize initial growth, and aqueous extracts in low concentrations could be used as growth bioregulators.