Bioassay results proved that several microalgae strains of the Mosonmagyaróvár Algal Culture Collection (MACC)enhances plant growth, due to their hormone content and other secondary metabolites. The aim of the current research was toimprove autumn growth winter survival of rapeseed (Brassica napus L. by treatment with two microalgae strains selected by bioassay results. Experimental plots were set up in Mosonmagyaróvár in 2010 and 2013. Winter rapeseed hybrid (B. napus L. cv. Orlando) plants were treated in 4-6 leaves stage with 0.3 g/L and 1 g/L suspensions of MACC-612 Nostoc entophytum Bornet & Flahault and MACC-430 Tetracystis sp. in missle of October. After the treatments, the following parameters were recorded: Chlorophyll-a and b, carotenoid, dry matter content of leves, average amount of autumn foliage, diameter of root collar, length of shoot tips, fresh and dry weight of root, and number of plants in autumn and spring. Both microalgae treatments significantly increased pigment concentration and dry matter content of leaves, number of fully grown leaves (13%-46%) and dry root weight (16%-36%). Treatments with 0.3 g/L and 1 g/L MACC-612 suspensions increased the length of shoot apices by 14%-18% and 25%-35%, respectively. Number of overwintered control plants decreased significantly in both years (31%), but there was no decrease in parcels treated with 1g/L of MACC-612 and MACC-430. Microalgae treatments could increase plant growth and survival, which contributed to the significant increase of thousand seed weight (18%-25%) and total yield (by 10%-24%).