This work investigates a hybrid polyester composite consisted of Curauá natural fibres and organophilic clay nanoparticles. A Taguchi method is used to identify the effects of fibre fraction (10, 20 and 30 wt%), alkaline treatmentconcentration (NaOH, 2.5, 5 and 10 wt%), treatment time (2, 4 and 8 h) and nanoparticle content (2.5, 5 and 10 wt%) on the mechanical behaviour of the hybrid composites under tension and three-point bending. X-ray, FTIR and microstructural analysis are performed to assess the treated and untreated fibre surfaces. The optimum combination of the process parameters for the tensile and flexural properties is: fibre content at 30 wt%, NaOH concentration at 5 wt%, treatment time at 8 h and nanoclay inclusions at 5 wt%. A mean tensile and flexural strength of 36.13 MPa and 32.55 MPa are obtained, whichrepresents percent increases of 39.22 % and 25.43 % compared to the polyester polymer in pristine condition.