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Alfalfa (Medicago sativa L.) is a forage species that is widely used in Canada but it causes bloat in cattle. Sainfoin (Onobrychis viciifolia Scop.), a condensed tannin containing legume does not cause bloat and in mixtures with alfalfa prevents bloat in grazing cattle. However, sainfoin cultivars developed for western Canada do not persist in alfalfa stands for long and do not regrow at the same rate as alfalfa in newly developed mixed stands. Nova sainfoin and three new sainfoin populations (3900, 3901 and 3902) were seeded in 2008 as monocultures and in mixtures with alfalfa, AC Grazeland at the Agriculture and Agri-Food Canada - Swift Current, Saskatchewan in the semiarid region of western Canada under rain-fed conditions to determine biomass yields and stand longevity under single cut for stockpile use or multiple cuts for pasture grazing or haying. Alfalfa and sainfoin were seeded in small plots (5 m x 5 m) to achieve a 50:50 proportion in the mixtures using a seeding rate of 5 and 15 kg ha-1 respectively. Mean DM yield of Nova sainfoin in five production years (4060 kg ha-1) was higher (p<0.01) than yields of the new sainfoin populations (3100 - 3300 kg ha-1) under the multiple cuts and also under single cut (2700 v 2000 kg ha-1). DM yields of alfalfa/sainfoin mixtures were 10 - 20% higher than the monocultures under both harvest regimes. DM yields in all stands were higher (p<0.01) under multiple cut regime than single cut in all production years. DM percent of sainfoin in mixed stands declined with age of stand but vigour of sainfoin under both harvest regimes were similar. The alfalfa/sainfoin mixtures may help improve pasture and hay production as well as stockpile hay in western Canada.