Alfalfa (Medicago sativa L.) is one of the most important forage crops worldwide because of its good forage quality and high adaptability. Seed yield is generally considered to be of secondary importance and is characterized by fluctuating yields with often poor seed yield and seed quality. A field study was conducted to determine if foliar B applications during anthesis increase seed set, seed yield, yield components, and improves seed quality in alfalfa. Boron solutions were applied at four rates (0, 400, 800, and 1200 mg B L−1) to field plots exhibiting no vegetative symptoms of B deficiency. Foliar B application increased the percent of pods formed per inflorescence by up to 52% compared with the control and there was no statistical significant difference between the three rates of B. The seed yield was increased by an average of 37 % compared with the control during the 2 yr and in both locations. Moreover foliar application with B improved seed germination and increased seed vigor which was increased by 27% in 2003 and up to 19% in 2004 compared with the untreated control. The 400 mg B L−1 treatment was found to have a positive response in most characteristics. The results obtained here suggest that the critical B levels for alfalfa used for forage production is below that for seed production and foliar B application can improve the seed yield and seed quality of alfalfa grown for seed production.