3D printed Polylactic acid (PLA) exhibts a visco-hyperelastic behaviour, which could be assessed through several techniques such as tensile tests and stress relaxation tests. In this research, the mechanical behaviour of Polylactic Acid (PLA) is studied experimentally and numerically. The force displacement curves of the material were obtained via uniaxial tensile test. In addition, stress relaxation test reveals a good deal of information to determine the time dependence of material behaviour as well as stress relaxation were performed. A constitutive model was elaborated for the hyper-viscoelastic behaviour of this material. Abaqus FEM soft-ware was used to adjust the unknown parameters in constitutive equations in order to fit the experimental data. Eventually, a good concordance is shown between the experimental and numerical results for material. Therefore, the proposed model could predict the nonlinear behaviour of 3D printed Polylactic acid (PLA) with accuracy.