Soybean [Glycine max (L.) Merr.] production has moved rapidly westward on the Canadian prairies, most recently arriving in southern Alberta. Adjusting row spacing (RS) and seeding density (SD) to maximize soybean productivity is well-documented for rainfed conditions but not where irrigation is obligatory. A 3 yr study was conducted at two irrigated locations in southern Alberta using two early-maturity [maturity group 00] soybean genotypes planted at two RSs and three SDs. Soybean reached 95% maturity in 114–132 d and only one of six growing environments experienced a killing frost prior to maturity. Wide rows led to 1 d earlier maturity for one genotype in all six environments and increased grain yield (5%–20%) in four out of six environments compared with narrow rows. Increasing SD from 30 to 80 seeds m^-2 generally led to increased pod clearance (from 5.0 to 8.4 cm in one environment) and grain (mean increase of 33%, from 2100 to 2800 kg ha^-1) and straw yield, but decreased seeds plant^-1 (from 94 to 46). Notwithstanding 9% lower cumulative corn heat units during the study, and an average 5 d longer maturity requirement at Lethbridge, soybean performance was equal to Bow Island in many parameters including grain yield. Our findings will help develop recommendations for new soybean growers in the irrigated region of southern Alberta.