Latent heat energy storage is one of the energy efficiency enhancing methods that has been emphasized in recent years. Materials used for latent heat storage having high storage capacity and absorbing and emitting heat by changing phase at a certain temperature are called phase change materials (PCMs). PCMs classify in three main groups: organic, inorganic, and eutectic. Organic phase change materials are mostly preferred than the other phase change materials due to the fact that they possess small-volume changes during the solid-liquid phase change process and higher latent heat of fusion. Encapsulation studies are carried out to increase the heat-transfer area for organic PCMs and to preserve volume change during phase change. Furthermore, the addition of the nano-structured materials into the organic phase change materials provides that the thermal conductivity be increased. At the same time, the use of organic phase change materials is becoming increasingly widespread with modeling studies on the thermal behavior analysis. In this study, a review of researches on encapsulation of organic phase change materials, thermal conductivity enhancement and modeling of thermal behavior reported in the last 20 years has presented.