In a field experiment, the effects of foliar application of silicon (sodium silicate 6mM) on yield and yield components of wheat cultivars (Shiraz, Marvdasht, Sirvan and Chamran) and also canopy temperature depression (CTD) under water stress conditions (F.C, 60 and 40% F.C.) were investigated during 2012- 2013 growing season using a split split plot as randomized complete block design with three replications. The results showed that both drought stress levels, especially 40% F.C, significantly reduced number of grains per spike, 1000 grain weight, grain yield, biological yield, harvest index and CTD of the examined wheat cultivars. The negative impact of drought stress was greater in Shiraz and Marvdasht cultivars. In contrast, foliar application of sodium silicate was associated with increased grain yield (16.11%), its components, leaf area index (20.15%) as well as CTD and this positive influence of silicon application was more pronounced under drought stress conditions. Furthermore, foliar application of silicon reduced canopy temperature and there was positive correlation between grain yield and CTD. Overall, it was concluded that foliar application of silicon under similar conditions to this experiment is potent to improve the grain yield of drought stressed wheat plants via an enhanced CTD or a reduced canopy temperature.