The greening of agriculture is currently a priority for its development. Intensive farming methods of the twentieth century have increased yields and fertility of soil agrocenoses through the use of fertilizers and plant protection chemicals. However excessive use of these chemicals has created serious environmental problems, namely water and soil pollution. One of the current tasks of researchers is looking of harmless ecological preparations for increased development and plant protection. Nitrogen fixing blue-green algae make a major contribution to the soil fertility. It has been suggested that blue-green algae assist higher plant growth by supplying growth substances. The benefits of algae, as sources of organic matter and fertilizer nutrients have led to their use as soil conditioners for centuries. Numerous studies have revealed a wide range of benefic effects of algal extract applications on plants, such as early seed germination, improved crop performance and yield, increased resistance to biotic and abiotic stresses. Based on the related, the aim of this study was to analyze the role of seed treatment with blue-green algal suspension on cucumber plants development. Our research was carried out in laboratory conditions. In experience have been involved 7 strains of algae (Nostoc flagelliforme (Berk et. Curt) Elenk, N. gelatinosum (Schousb) Elenk., Cylindrospermum licheniforme (Bory) Kьtz. f. licheniforme, C. licheniforme (Bory) Kьtz. f. alatasporum Kondrat., Anabaena variabilis Kutz., A. propinqua Setchell. et Gardn. and Anabaenopsis sp.). Algal biomass was inoculated to the soil in fresh (wet) and dry form in an amount of 3 kg/ha and 1 kg/ha respectively. Initially the seeds of cucumbers were treated for 24 hours with algae solution of 1 g/l dry and wet biomass of species mentioned above. The seeds were planted in a growth supports to a depth of 2–3 cm exposed to daylight and watered daily, at 25–27˚C temperature. As a control sample served untreated seeds. Within 31 days we measured length of stems and leaves. The treated seeds demonstrated faster germination, where used suspension of wet biomass of Nostoc flagelliforme, N. gelatinosum, Cilindrospermum licheniforme f. licheniforme, Anabaena variabilis, and the suspension of Anabaenopsis sp. dry biomass. Most plantlets sprang up after 5 days from planting, with the exception of the plantlets treated with wet algal biomass of Nostoc flagelliforme, Cylindrospermum licheniforme f. alatasporum and Anabaena propinqua species. The seed treatment with dry biomass suspension demonstrated better results in case of stem and leave growth. The best results were obtained in case of seed treatment with dry biomass of Anabaena propinqua, Cylindrospermum licheniforme f. alatasporum, Cylindrospermum licheniforme f. licheniforme: stem length after 31 days cultivation increased by 29,6% compared with the control group and reached 54,3 cm, 51,0 cm and 47,7 cm respectively, while the control sample was 38,2 cm length of the plant. In the case of seed treatment with wet biomass suspension best results were obtained in samples with Anabaenopsis sp. Biomass: after 31 days the plant length was 50 cm, while in the control sample was only 38, 2 cm. Also good results were obtained in case of treatment with Nostoc flagelliforme suspension: average plant length achieving growth up to 49,7 cm, which is 1,3 times higher than untreated plants. Thus we can state that the best results could be obtained in the case of cucumber seeds treatment with dry microalgal biomass suspension.