Given developments in the construction material industry, existing knowledge of concrete confined with fiber-reinforced polymer (FRP) must be validated for newly developed FRP-type materials. Polyethylene terephthalate (PET), which has a high ultimate tensile strain, is a relatively new type of fiber. Given the limited number of studies on PET-FRP, the goal of this study is to observe and define the mechanical behavior of PET-FRP-confined concrete specimens subjected to monotonic/cyclic compression loading. In this study, the behavior of concrete confined with PET-FRP is compared with the behavior of concrete confined with other types of FRP. The general form of the compression stress-strain relationship of PET-FRP-confined concrete consists of two parts that are connected with a transition part, which is similar to concrete confined with other FRP types. Additionally, to understand whether available models are able to predict the compressive behavior of PET-FRP-confined concrete, the predictions from four models are compared with the corresponding test results. The results indicate that the compression stress-axial strain relationship of PET-confined concrete is not predicted in a sufficient manner using the four models. (C) 2014 American Society of Civil Engineers.