This study investigates the effect of fibre length on the mechanical performance of epoxy bio-composites reinforced with Gigantochloa Albociliata (Malaysian honey bamboo) fibres. The composites were fabricated via hand lay-up using short fibres (3 cm, Sample II), medium fibres (6 cm, Sample III), and long fibres (12 cm, Sample IV). All fibres underwent 6 wt% NaOH treatment under heterogeneous conditions, which involved either immersion for 24 hours at 65 °C, followed by oven drying, or extended immersion for 48 hours at room temperature with subsequent air drying. Fibre volume fractions ranged from 5% to 20%. Tensile tests revealed a consistent improvement in strength and stiffness with increasing fibre length and content. Short-fibre composites (Sample II) achieved up to a 43.2% increase in tensile strength over neat epoxy, while medium fibres (Sample III) recorded gains of 49.0%. The most pronounced enhancement was observed in the long-fibre composites with 48 hours of treatment (Sample IV), where the 20% loading (IV-D) achieved the highest tensile strength (53.71 MPa) and Young’s modulus (1788.1 MPa), reflecting improvements of 115.8% and 62.6%, respectively, compared to neat epoxy (24.9 MPa, 1100.5 MPa). However, ductility declined, with strain at break reducing from 3.7% in neat epoxy to 1.98% in composite IV-D, reflecting the trade-off between stiffness and flexibility. These results confirm fibre geometry and treatment protocol as critical design factors, with longer fibres providing superior reinforcement efficiency. Overall, Gigantochloa Albociliata demonstrates strong potential as a sustainable reinforcement for high-performance bio-composites in load-bearing applications.