This research examines mechanical properties and optimization of HCs made from Calotropis gigantea, date palm leaf fiber (DPLF), and tamarind seed shell powder (TSSP) utilizing epoxy resin utilized as matrix material. Nine unique constructions was produced utilizing varying TSSP of (0, 6, and 12 wt%) to assess the effects on flexural strength, impact resistance and tensile strength. TSSP underwent alkali method and was evaluated using XRD, particle size analysis and FTIR to improve their compatibility with polymer matrix. Fibers and TSSP were treated with 5 wt% NaOH for 4 h at room temperature. Samples were washed to neutral pH and oven dried at 60 °C for 24 h. Date palm leaf fibers and Calotropis gigantea fibers (CGF) were subjected to alkali procedure to enhance interfacial adhesion. The composite technique utilized Taguchi L9 OA for design optimization. Taguchi L9 OA reduced experimental runs while effectively studying three factors at three levels. This approach minimized cost and material use without compromising statistical reliability. Mechanical tests demonstrated that use of TSSP markedly enhanced overall performance with S9 (6 wt% TSSP) displaying the best flexural strength (95.88 MPa), impact resistance (9.97 kJ/m²) and tensile strength (61.53 MPa). The MEREC–RAMS methodology were utilized to rank composite with S9 designated as the superior configuration. At 6 wt% TSSP, filler dispersion is uniform, enhancing stress transfer efficiency. At 12 wt%, particle agglomeration likely caused stress concentration and reduced mechanical performance. Comparisons with various MCDM approaches (WASPAS, MARCOS, PIV, and EDAS) confirmed the dependability of the rankings with S9 consistently achieving the highest performance. ANOVA confirmed that TSSP content significantly influenced mechanical properties at a 95% confidence level. This validates the reliability of the optimization results. The sensitivity analysis confirmed the resilience of the MEREC–RAMS methodology, since rankings remained consistent despite fluctuations at criterion weights. The combined action of calotropis gigantea, date palm leaf fiber, and TSSP, together with enhanced interfacial bonding, resulted in mechanical characteristics of hybrid composites. This study presents a tri-hybrid composite system combining Calotropis gigantea fiber, date palm leaf fiber, and TSSP with integrated Taguchi and MEREC–RAMS optimization. The simultaneous experimental and multi-MCDM validation approach distinguishes it from previous binary composite studies. These outcomes underscore promise of CDT composites as sustainable materials, high-performance for diverse industrial uses at construction, aerospace and automotive industries.