The development of new methods enhancing the growth and yield of cereals is still needed in crop production due to their great importance in human diet and as livestock fodder. In our study, new fertilizer-biostimulators with micro- and macroelements and extract containing lipochitooligosaccharides (LCOs) produced by Rhizobium leguminosarum bv. trifolii were used for stimulation of growth of barley and triticale in greenhouse conditions. The preparations were applied at the tillering and shooting stages, whereas plant traits were studied at flowering and at full maturity. The best results were recorded after the joint treatment of the plants with LCOs and mineral fertilization. The application of such a mixture significantly increased the length and mass of roots at flowering in both studied species. A beneficial effect of the treatment was also observed in barley and triticale yields. At full maturity, the grain mass per plant was significantly enhanced, which was the effect of an increased number of grains per ear and increased mass of 1000 grains.