The application of algal bio fertilizers in the cultivation of agricultural crops is efficient and necessary, due to their significant benefits for the soil (characterized by the improvement of soil structure, the increase of water maintenance capacity and biogenic content etc.) and crop plants (by providing nutrients, stimulating seed germination, increasing productivity and improving biomass quality, protecting against pathogens, etc.). The selection of algal bio fertilizers for crop cultivation should be based on the idea of using of massively growing in the soil species. These algae species should be able to supply for a long time the soil with nutritive and biological stimulating substances for plants and soil micro biota. The most common group of algae that meets these requirements is the genus Nostoc, which species are frequently found in various soil types and under different conditions. In this paper are presented the results of the study of algal bio fertilizers effects on the cultivation of tomatoes in greenhouse conditions. The research was carried out under greenhouse conditions at the company “AŢ ZIM” SRL, Republic of Moldova during spring – autumn, in 2 sectors (experimental and control) with an aria of 20 m2 per sector. The living biomass of Nostoc flagelliforme, N. gelatinosum and N. puntiforme, at the dose of 6 kg / ha, was distributed equally on experimental sector 15 days after planting the seedlings in greenhouses; the additional administration of the bio fertilizers at the same dose was performed every 22 days after. The chemical fertilizer nitroamophos (NH4H2PO4+NH4NO3+KCL) was administered in both sectors in the same concentration on the 40th day and on the 100th day, after the initial inoculation of the algal bio fertilizer. During the experiments, the pH and the total nitrogen content in the soil, the height and the yield of each tomato plant have been monitored. The administration of algal bio fertilizers induced positive changes in soil properties, characterized by a slight change of pH in alkaline direction (soil pH in the experimental oscillated within the limits of 7.08-7.98, and in control sector - in the range of 6.59-7.48) and an increase in the total nitrogen soil content (0.28% - 1.31% in the experimental sector compared to 0, 28% -1, 11% in the control sector). The administration of algal bio fertilizers had a positive impact on tomato growth in the first 44 day (experimental plants had a height of 137.50 ± 4, 22 cm, and in the control sector – 133.50 ± 6.30 cm). Further the increase in height has slowed in experimental sector and at 110 day of analysis the height of the plants in the experimental sector was lower compared to the control (154, 16 ± 12.23 cm, and 164.46 ± 4.64, respectively). The administration of algal bio fertilizers had a positive effect tomato yield: 16, 33 ± 1, 48 tomatoes / plant in experimental plants, compared to 13, 53 ± 1, 22 tomatoes / plant and in the control variant. In conclusion, we can state that the application of algal bio fertilizers have a positive effect on soil properties and tomato plant growth and yield.