Single crystals of B2 Fe-39mol%Al without frozen-in vacancies were deformed in compression in the temperature range from room temperature to 1073K in order to investigate the temperature dependence of yield strength and the slip transition behavior. The positive temperature dependence of yield stress was found in this alloy. The peak temperature is not strongly dependent on compression axis, and is located at approximately 0.5Tm, where Tm is the melting point of Fe-39mol%Al alloy. In addition the slip transition from 〈111〉-type of 〈001〉-type occurs macroscopically around the peak temperature for all compression axes. Non- slip is identified to operate slightly on (1̄01) plane even below the peak temperature by the two-surface trace analysis. Moreover it was observed that some of  dislocations decompose into  and  dislocations on (1̄01) plane at temperatures below the peak, suggesting that critical shear stress for  slip increases with increasing temperature. Thus it is clarified that the positive temperature dependence of yield stress is closely associated with the slip transition behavior.