As the soft plastic is an abundant material in the Municipal Solid Waste (MSW) mass, and considering that it acts as a reinforcement element, its influence on MSW shear strength has been a target of constant study. The variables involved in this study are the amount of plastic, its inclination to normal and shear stresses, its tensile strength, the issues related to the mobilization of strength stresses by the plastic, etc. The present paper aims to study the variables involved into the contribution of soft plastic on MSW shear strength, through the execution of direct shear tests to samples of sand combined with plastic bag strips. Some of these strips were previously immersed into leachate at different periods of time, in order to provide information about the influence of this substance on the specimens shear strength. It is expected through this study to help the understanding of the soft plastics influence on the MSW behavior, contributing to improve the design, construction and storage capacity of sanitary landfills.