Natural fibers provide numerous advantages like lightweight, affordable, high strength-to-weight ratio, eco-friendliness, recyclable and so on. These attributes have propelled the utilization of natural fibers in composite to forefront of industrial innovation primarily because of their potential to drive sustainable initiatives and minimize carbon footprints. Among these, Luffa cylindrica stands out as a promising candidate to supplant synthetic fibers in composite materials facilitating sustainable resource deployment. The raw Luffa fibers were alkalized and converted into short fibers that were used for making Luffa fiber layers. Hand layup technique is used for fabrication of single-layer (1L), double-layer (2L), and quadruple-layer (4L) short Luffa fiber epoxy composites. Effect of fiber weight percentage (wt.%) on flexural, tensile and inter-laminar fracture (Mode II) of the composites was analyzed in universal testing machine maintaining the ASTM standards. The mechanical and thermal properties of a high weight percentage composite appeared to be superior to those of a low weight percentage composite. Tensile strength (26.92 MPa), flexural strength (35.24 MPa) and inter-laminar fracture energy (807.62 J/m2) are all high for the 4L Luffa/epoxy composite. The thermal analyses of composites were conducted using thermogravimetric analysis and observed that with the increase in fiber wt.%, the thermal stability and activation energy of composite increases. Four layer Luffa composite has found to have highest activation energy about 97.06 kJ/mol and thermal stability about 300–350 °C than other composites. The significance of current work reveals that this fiber composite may have high applications in various technical fields.