Protein-based bioplastics are materials obtained with renewable natural components that present huge benefits as their technological capacity in a wide range of purposes. Besides, pea protein isolate and glycerol seem to be an excellent combination to create new bioplastics due to their fantastic processability and hydrophilic character. This is achieved by a thermomechanical process of two stages: mixing and injection moulding. The goal of this work is to study the preparation of pea protein-based bioplastics by the evaluation of the influence of the processing stages on the properties of the final bioplastics obtained. These bioplastics were studied evaluating different processing parameters (mixing speed and time) by assessing their influence on the protein-plasticizer blend with the analysis of the microstructure, as well as the rheological and mechanical behaviour. In addition, water uptake tests were also performed. The results showed that short and long mixing times and high mixing speeds (50 rpm) led to heterogeneity. While, intermediate mixing speeds (30 rpm) and short mixing times (1 and 10 min) were found to be suitable to obtain bioplastics with good mechanical properties.