Various ductile sheet materials are currently being considered to retrofit existing concrete walls to mitigate the effects of external blast. In this paper, the blast mitigation of the soft and rigid sheet retrofit systems of reinforced concrete walls is studied. Different types of thin sheet retrofits, such as steel, rubber, polyurea, and polymer-fiber composite sheets, were examined by using a series of full-scale quasistatic tests to evaluate their static resistance. Finite-element modeling was performed to study the straining action of the wall elements, including the retrofit system. Nonlinear single-degree-of-freedom dynamic analysis was performed to calculate the blast response and study the mitigation effects of the various sheet materials considered. Experimental results showed that all retrofits exhibited significant energy absorption after a support rotation of 10°. Finite-element models were able to closely predict the static resistance function of these retrofitted walls. Parameters such as friction coefficient, end-connection gap due to slack in the sheet, and connection stiffness were investigated. It was found that by increasing the initial gap to account for slack, the membrane action is delayed, which increases the ductility of the wall and the area under the resistance-displacement curve. Increasing the friction and the stiffness of the end-connection increased the resistance and the overall energy absorption of the retrofitted wall system.