To evaluate effect of photosynthate availability under terminal heat stress on yield and yield components of wheat, this research was conducted in a split plot experiment based on randomized complete block design (RCBD) with three replications at the Research Farm of Islamic Azad University of Ahvaz in 2015 cropping season. Treatments were defoliation in four levels: removal of two upper leaves, flag leaf removal, complete removal of spikelet at one side of spike and control (non-manipulated) which assigned to main plots and three planting date including (Nov.21st, Dec.5st and Dec.21st) to subplots. Results showed that defoliation had significant effect on number of grains/spike, 1000 grain weight, grain yield, biological yield and harvest index at one percent probability level. planting date also affected number of spike/m2, number of grains/spike, 1000 grain weight, grain yield, biological yield, and harvest index significantly at one percent probability level. The interaction effect of defoliation and planting date on the number of grains/spike, 1000 grain weight, grain yield, biological yield and harvest index was also significant. The highest grain yield (5691 kg.ha-1) belonged to the control treatment (no defoliation) at first planting date (Nov.21st). This was due to the not coinciding filling periods to terminal heat stress of growing season where maximum assimilates were produced. The lowest grain yield (2123 kg.ha-1) belonged to delayed sowing and removal of spikelet at one side of spike. Maturity of plants during 3rd planting date (Dec.21st) was coincided to heat stress and thus reduced assimilate production.