Durum wheat is indigenous to Ethiopia and is planted extensively by small-scale farmers. Drought stress is one of the major constraints faced by farmers. The main aim of this study was to evaluate the expression of drought tolerance in the parents and F 1 progeny of a six by six half diallel cross, made with two drought tolerant, two intermediate, one moderately susceptible and one susceptible parent. Parents and the 15 F1 hybrids were evaluated at a maximum of 35 and 70% available soil moisture in a glasshouse. Analysis of variance revealed significant variability for yield, yield components, and drought tolerance measurements. Drought tolerance was expressed in the crosses involving tolerant parents, and was controlled predominantly by additive genes. The diallel analysis revealed that mean squares for both GCA and SCA were significant at both moisture levels. GCA: SCA ratios indicated predominance of additive gene actions for all characteristics measured, although non-additive genes also played a role, particularly in the absence of stress. GCA effects were mainly positive. GCA effects as well as their rankings were significantly affected by moisture stress. SCA effects were also mainly negative. Considerable variability in SCA values between the two moisture levels were found.