The mechanical properties of polyester hybrid composites reinforced with treated and untreated coir fibres and 15 wt.% of cement microparticles at different locations were investigated in this work. A Full Factorial Design (2 1 3 1 ) was conducted to identify the effect of the chemical treatment of coir fibres and location of cement inclusions on the tensile (and flexural) strength and modulus. In general, the alkaline treatment led to increased tensile properties and flexural strength compared to untreated fibre composites. The inclusion of cement particles, especially added throughout the whole sample, increased the tensile and flexural strength and tensile modulus of untreated coir fibre composites. A significant increase in flexural modulus was observed only in composites made with treated coir fibres along with the incorporation of cement particles in the whole sample.