In the present work, E-glass/polyester composite laminates were manufactured in a customized resin transfer mould (RTM) with different layers of fiber at selected resin injection pressures. Experiments were performed employing full factorial design to study the influence of number of fiber layers and resin injection pressure on mechanical properties of the composites. Analysis of variance was implemented to study the interaction effect of process parameters on multi-responses namely tensile, flexural and impact strengths. Taguchi method based grey relational analysis was used to determine optimal control factors for the responses. Numbers of fiber layers and the injection pressure have significance with respective 73.96% and 16.57% contributions on the grey relation grades of the three responses. An optimal working condition was suggested to produce quality composite. In addition, mathematical models for the mechanical properties were also developed using the experimental results.