The objective of this study was to evaluate the effects of dietary mannan oligosaccharide (Bio-Mos) supplementation on reproductive, productive performance and milk production of APRI line rabbit does under high ambient temperature. A total of 40 APRI line rabbit does, 8-9 months old, were divided into four experimental treatments (10 each). Rabbit does were fed ad libitum the basal diet supplemented without (control), with 0.5, 1 or 1.5 g mannan oligosaccharide (Bio-Mos) /kg diet. Animals were provided with water freely. The average daily temperature and relative humidity inside the rabbitry were 31.6±3.8 °C and 77.5±4.8%, respectively. Under heat stress conditions, does weight gain at gestation significantly increased (P<0.001) with increasing dietary MOS supplementation. Pregnant rabbit does given diet containing 1.5 g MOS /kg diet showed the highest weight gain than those fed other dietary MOS levels during the pregnancy period.Daily feed intake of pregnant and lactating rabbit does increased (P<0.05) with increasing dietary MOS level, where rabbit does fed diet containing 1.5 g MOS /kg diet recorded the highest values. The feed conversion ratio was significantly improved (P<0.001) with rabbit does fed diets containing different MOS level (0.5, 1.0 and 1.5 g) during lactation period. The mortality rate of the pups during the lactation period was higher in the control diet compared to diets with 0.5, 1.0 and 1.5 g MOS (32.11 % vs. 25.82, 18.37 and 17.77%; P<0.01, respectively), which could be due to lower milk yield of rabbit does fed unsupplemented diet. Rabbit does fed 1.0 and 1.5 g MOS/kg diet recorded the highest values of letters weights, during the first three weeks. The same trend was obtained at weaning. Rabbit does fed 1.5 g MOS/kg diet recorded the highest net revenue, followed by those fed 1.0 g MOS/kg diet. It could be concluded that supplementing MOS in rabbit does diet significantly improve the overall productive and reproductive performance of rabbits does during pregnancy and lactation periods, in addition to depressing the mortality of pups under high ambient temperature during summer season in Egypt. Therefore, it could be recommended providing rabbit does diet with MOS up to 1.5 g/kg diet is advisable in hot climates, Egypt.