In the present study, application of Ecklonia maxima extract (Kelpak SL – a water soluble concentrate) was optimized and its impact on yield, nutraceutical and nutritional potential of Phaseolus vulgaris L. (var. Aura and Toska) was measured. The study was carried out in 2012 and 2013 in Poland. During the growing season, 0.2% and 0.4% solution of Kelpak SL was applied by single and double spraying of plants. These four treatments with Kelpak SL were compared with the control, where no biostimulator was applied. Kelpak SL treatments stimulated the yield of both cultivars studied. The application of E. maxima extract had no effect on the content of starch, free sugars or proteins in seeds of either of the tested cultivars. The highest level of phenolics was found for double sprayed Toska plants. All the tested variants of Kelpak SL application significantly increased the content of anthocyanins in the seeds. Also, both the reducing power and antiradical ability of Aura seeds were elevated in all the studied treatments. E. maxima extract is a natural, environmentally friendly and safe preparation increasing the yield and nutraceutical quality of beans without any negative effect on their nutritional quality. Keywords: Antioxidant capacity, Ecklonia maxima, Kelpak SL, Nutrients, Phaseolus vulgaris L., Yield