The fracture properties of Fe-40at%Al alloys fabricated by reactive hot-pressing was investigated under various types of testing conditions. Fracture toughness of the alloys exhibited significant loading rate dependence due to the environmental effect. The grain boundary cohesion in the non doped alloy was inherently weaker than its cleavage strength. In addition, the environmental embrittlement of the alloys rapidly accelerated at a critical applied stress intensity factor.