There has been much effort to provide eco-friendly and biodegradable materials for the next generation of composite products owing to global environmental concerns and increased awareness of renewable green resources. An increase in the use of natural materials in composites has led to a reduction in greenhouse gas emissions and carbon footprint of composites. In addition to the benefits obtained from green materials, there are some challenges in working with them, such as poor compatibility between the reinforcing natural fiber and matrix and the relatively high moisture absorption of natural fibers. Green composites can be a suitable alternative forpetroleum-basedmaterials. However, before this can be accomplished, there are a number of issues that need to be addressed, including poor interfacial adhesion between the matrix and natural fibers, moisture absorption, poor fire resistance, low impact strength, and lowdurability. Several researchers have studied the properties of natural fiber composites. These investigations have resulted in the development of several procedures for modifying natural fibers and resins. To address the increasing demand to use eco-friendlymaterials in different applications, an up-do-date review on natural fiber and resin types and sources, modification and processing techniques, physical and mechanical behaviors, applications, life-cycle assessment, and other properties of green composites is required to provide a better understanding of the behavior of green composites. This paper presents such a review based on 322 studies published since 1978.