The aim of the studies was to evaluate the influence of sowing rate, foliar fertilization (Basfoliar fertilizer 6-12-6) and chemical composition on the mechanical properties of narrow- leaved lupine seeds of cultivars Bojar and Regent. Single seeds were burdened in the direction perpendicular to the parting plane of cotyledons with constant speed 10 mm∙min-1. The crop year and cultivar have significantly differentiated the value of all the analyzed strength parameters of narrow-leaved lupine seeds. The seeds of cultivar Bojar had significantly higher values of all the strength parameters. The designated strength parameters of lupine seeds were negatively correlated with ash content, fiber and protein except for the destructive force. They were also positively correlated with the fat content.