Precast concrete sandwich panels are a structural system consisting of concrete layers with insulation layers in between. The concrete layers are connected through the insulation with specially designed connectors. For engineers to properly design and analyze the strength characteristics of sandwich panels and their connectors, the engineers need to obtain recommendations from the individual connector manufacturers, which can be a very rigorous process. This project tested eight full scale precast concrete sandwich panels with two concrete layers on either side of an insulation layer with connectors concentrated at either end of each panel. The objectives of this project were to evaluate the interaction between the two concrete layers and how well the connectors transferred forces between the layers (percent of composite action) and to validate simplified methods of predicting properties of the panels by comparing the predicted panel properties to the results of the testing series. Additionally, this study evaluated the panel’s different thicknesses and lengths and compared their results.