Plant fibers are increasingly used in fabricating polymer composite components useful in the automotive, construction, and aerospace industries. This surge in the usage of plant fibers in different industries is owing to the improved understanding of the toxicity of synthetic fibers. It is essential to point out that “Humans need earth, not earth needs humans” therefore policymakers and researchers are working on replacing traditional materials with green materials. Plant fibers are green materials with many advantages over synthetic materials, such as easy processing, reduction of CO2 emissions, biodegradable, recyclable, good thermomechanical properties, and better compatibility with human health. Therefore, plant fibers are extensively used as a modifier for polymers. The drawbacks of plant fibers are the presence of OH groups in their basic structure and the presence of amorphous components. Both these drawbacks can be reduced by chemically treating the fibers. Further coupling agents can be used to increase the compatibility between the fiber and polymer. It is reported that incorporating fibers (non-continuous or continuous), and fiber mats as a reinforcement for polymers improve the mechanical, thermal resistance, thermal conductivity, and surface properties. Accelerated aging studies also reported favourable results for the use of plant fiber-based composites for long-term outdoor applications. However, plant fibers have lower strength and are hydrophilic compared to synthetic fibers, more research is required to overcome fully these drawbacks. This review examines and discusses the fundamentals of plant fiber, its processing, drawbacks, recent research trends, composites properties, prospects, and potential applications.