Constructed wetlands (CWs) are widely recognized as nature-based solutions for wastewater treatment, offering various socio-economic and ecological benefits. However, the sustainable management and disposal of waste biomass generated from CWs have received limited attention. Owing to the rich lignocellulosic proportions, the harvested vegetation can potentially serve as a feedstock for various value-added products, including natural fiber-reinforced polymeric composites (NFRPCs). In this context, for the first time, we present a comprehensive review exploring different valorization routes employed to gainfully utilize waste biomass from CWs. The study discusses various value-added products developed so far from the waste biomass of CW. Biogas generation and bioethanol production are the most commonly explored valorization pathways. However, the commercial implementation of these value-added products is stalled by factors such as growth conditions, pretreatment, moisture content, process conditions, and limited energy recovery efficiency. Furthermore, this article introduces a novel class of sustainable materials, namely NFRPCs, developed for the first time by utilizing waste biomass from CWs as a reinforcement element in the polymeric matrix. A detailed analysis of the physical, mechanical, structural, and crystallographic characteristics of Canna indica (CI)-reinforced polypropylene (PP) composites is also discussed to evaluate their pertinence for structural applications. Additionally, we provide an in-depth review of natural-fiber-reinforced polypropylene composites, comprising single-fiber composites, hybrid fiber composites, and composites reinforced with organic/inorganic fillers. This comprehensive review emphasizes the potential of utilizing waste biomass from CWs as a sustainable feedstock for developing NFRPCs. It also highlights the promising prospects of NFRPCs as a sustainable substitute to synthetic fiber-reinforced composites, contributing to a circular economy and a greener future.