In this study, modern retrofit materials were implemented in an attempt to improve the out-of-plane behavior of URM walls. The laboratory testing of the retrofitted walls was divided into two phases of study: slender walls where wall behavior was controlled entirely by bending, and non-slender walls where the presence of arching action was observed. In both phases of study the retrofit systems were found to be effective in improving the behavior of the URM walls. Additionally, the study sheds light on the effect of slenderness on wall capacity, and the relationship between slenderness and retrofit effectiveness.