Sterility has emerged as a widespread problem for wheat (Triticum aestivum) production in South and South-east Asia. Whilst boron (B) deficiency is commonly associated with sterility in wheat, the expression of sterility is complicated in rainfed conditions by a number of environmental factors including water stress. A field experiment was conducted to examine the effect of water stress on B response of wheat genotypes on a low B soil (0.087 mg B kg-1soil) at Chiang Mai, Thailand (18°45′ N, 99° E) during the dry season from November to March. The experiment consisted of three factors arranged in a split-split plot design with two levels of irrigation: water stress (I−) and full irrigation (I+) in main plots, two levels of B: 0 kg (B0) and 1 kg B ha-1 (B+) as borax in sub plots and four wheat genotypes: SW 41, BL 1022, UP 262 and Sonora 64 in sub–sub plots. Water stress was applied by discontinuing irrigation in I− treatments after the double ridge stage. In all genotypes, above ground biomass was decreased by I−, but not by B deficiency. Significant B×genotype interactions were detected for reproductive growth. SW 41 and BL 1022 strongly responded to added B with relief from B deficiency symptoms at anthesis and improved grain set index (GSI), grains ear-1, ears with grain and grain yield at maturity. By contrast, Sonora 64 could set grain well at B0 and did not show any response to added B with respect to these parameters. Grains ear-1 of SW 41 and BL 1022 was not affected by full irrigation at B0, but were significantly increased when fully irrigated with added B. In all genotypes, B concentration of the flag leaf and the ear at booting and at anthesis was significantly higher in B+, but was not affected by irrigation. Boron × irrigation interactions detected in this study indicate the possibility of the influence of water stress on the severity of wheat sterility in South and South-east Asia.