The development of mitigating agents to counter injuries induced by radiation is as important as the development of radioprotective agents. This study reports the ability of diallyl sulphide (DAS), a naturally occurring organosulfur compound, to mitigate radiation-induced mortality and injuries to the hematopoietic system in whole-body irradiated mice. Intraperitoneal administration of a single dose of DAS (160 mg/kg body weight) 2 hours after 9 Gy whole-body irradiation resulted in 37% animal survival as opposed to 100% mortality in the irradiation-only group, improved general conditions with no visual signs of sickness, and body weight loss. Restoration of spleen body weight index by DAS in animals exposed to sublethal dosages (2 and 5 Gy) of whole-body irradiation increased endogenous spleen colony-forming units and increased bone marrow cellularity indicated enhanced hematopoietic recovery, which was supported further by recoveries in lymphocyte count. Further studies to elucidate the mechanism of action of DAS are warranted to design effective protocols for mitigation of radiation injuries using compounds like DAS.