The aim of this study was to determine the effect of different proportions of Medicago media Pers. in mixtures with Festulolium braunii (K. Richt) on the yield and nutritional value of green fodder. A qualitative analysis of fodder included the determination of the concentrations of acid detergent fiber (ADF) and neutral detergent fiber (NDF), and the relative feed value (RFV) which combines feed intake with digestibility and supports an effective evaluation of roughage. A small-area field experiment was conducted in 2011-2012 at the Agricultural Experiment Station owned by the University of Warmia and Mazury in Olsztyn (Poland). The experiment was established on mineral soil of quality class IVa and very good rye complex. The percentage of alfalfa seeds in the mixture was 30, 50 and 70% relative to the total mass of seeds of pure-sown species. Control treatments were pure-sown alfalfa (100%) and pure-sown Festulolium (100%). It was found that alfalfa had high competitive advantage over Festulolium – the share of the former species in mixtures was considerably higher than the percentage of seeds sown. The yield of alfalfa/Festulolium mixtures was significantly higher than the yield of pure-sown Festulolium and similar to the yield of pure-sown alfalfa. The introduction of alfalfa to the mixture decreased the NDF content of biomass, thus improving fodder quality. Varied proportions of alfalfa seeds in mixtures had no significant effect on the analyzed parameters of feed quality.