Nowadays, environmentally friendly composites are encouraged by the worldwide community due to their easy recyclability and degradability. So, natural fibre-based composites are capturing the market exponentially. The vast application opportunities in the manufacturing sector, such as automobiles, marine, piping, and grocery items, are leaders in applying natural fibre components. Several usual fibres like rice, oil palm, coconut, and kenaf have been successfully implemented and have better mechanical properties. Additionally, reinforcing natural fibre inside high-density polyethene (HDPE) plays a key role among many polymers as it acquires numerous benefits, such as strength and excellent chemical stability. HDPE has several other advantages, such as being durable, lightweight, and machine-friendly, making it usable in medical, construction, maritime, and food. As a result, this review thoroughly discusses the mechanical characteristics of this reinforced in HDPE and various parameters affecting the structural features of polymer composite, such as loading, fiber dimensions, and fiber structure. A critical observation is also done to understand the broader effect of the mechanical properties on varying the fibre wt.% and loading. This review article also outlined the survey and collected earlier works demonstrating natural fibres' mechanical properties and their composites. Thus, there is an extensive availability of knowledge for additional investigations into the characteristics of synthetic fibres.