Abstract <p>Natural fiber-reinforced composites are gaining attention as sustainable alternatives to synthetic materials due to their renewability, biodegradability, and favourable strength-to-weight ratio. Hybrid bio-composites are fabricated using luffa and coir fibers with cashew nut shell liquid (CNSL) resin through the hand lay-up method. Six composite specimens (S1-S6) with varying fiber volume fractions, luffa-coir ratios, and sodium hydroxide (NaOH) treatments are prepared and evaluated for mechanical, structural, and microstructural performance. Mechanical characterization revealed that alkali treatment significantly enhanced properties. Among all specimens, Sample S5 (40% fiber, 30% luffa, 10% coir, NaOH-treated) demonstrated the greatest improvements, recording a tensile strength of 25.9 ± 1.4&#xa0;MPa, flexural strength of 4.1 ± 0.3&#xa0;MPa, hardness of 86 Shore-D, and a Young’s modulus of 4.08<b> ± </b>0.22&#xa0;MPa, compared to untreated samples, which showed tensile strength between 8.9 ± 0.7 to 11.3 ± 1.0&#xa0;MPa and flexural strength up to 2.8 ± 0.2&#xa0;MPa. Water absorption analysis indicated a reduction to 3.78% for S5, compared to 17.42% in untreated samples, confirming improved resistance to moisture uptake. Microstructural analysis verified cleaner surfaces, reduced voids, and stronger fiber-matrix adhesion in treated composites. Furthermore, finite element analysis (FEA) of a fridge stand prototype under a 980 N load confirmed structural reliability, with a maximum stress of 3.76 × 10⁵&#xa0;Pa, strain of 1.88 × 10⁻⁶ Pa, and minimal deformation of 9.1 × 10⁻⁷ m. These findings demonstrate that luffa–coir composites reinforced with CNSL resin and optimized through alkali treatment offer enhanced mechanical properties and durability, positioning as promising eco-friendly materials for structural, automotive, and domestic applications.</p> Graphical Abstract <p></p>