Abstarct: This experiment was aimed to study the interactive effects of drought stress and ultrasonication on growth and yield of cowpea. Drought stress is one of the important facrors decreasing the yield of plants especially pulse crops. baxsed on a few reports, ultrasonication is expectedto have a positive effect on drought-stressed crops. This experiment was as factorial baxsed on randomized complete block design with 3 replications which was conducted in research farm of Shahrood University of technology in 2014. Treatments were drought stress [control (full irrigation), no irrigation after flowering and dough stages] and ultrasonication duration [control (no irradiathion), 1.5, 3.5, 5.5, and 7.5 minutes]. Results indicated that drought stress decreased plant height, stem dry weight, leaf relative humidity, leaf area index, number of branch, number of pod, 100 seed weight, grain yield and biological yield, but increased grain protein content. Ultrasonication increased plant height, stem dry weight, leaf relative humidity, number of branch, number of pod, 100 seed weight, grain yield, biological yield, and grain protein content. For most of traits, the best irradiation duration was 5.5 minutes and 7.5 minutes had negative effect on most of the traits. The interaction of drought and ultrasonication appeared to be significant on number of pod, chlorophyll and leaf dry weight. The simple and interactive effects of factors were not significant on number of seed in pod.