This study aims to determine the effect of pre-strain on the mechanical properties of CP-Ti and Ti-6Al-4V materials, especially on tensile strength and Young's modulus. The materials used are CP-Ti Grade 4 and Ti-6Al-4V grade 5 with cylindrical geometry measuring 500 x 2.5 mm, which are then machined to conform to ASTM E8 standards using a diamond cutting machine. Furthermore, the test was carried out using a Shimadzu Autograph Machine with Tensile Test Grip by giving pre-strain to the test specimen with variations of 6%, 11%, and 15% for CP-Ti, and 6%, 9%, and 12% for Ti-6Al- 4V, where each value represents the elastic, ultimate and necking regions after the ultimate occurs. Based on the experiments conducted, it was found that the pre-strain treatment did not significantly affect the tensile strength. In fact, it tended to decrease the tensile strength along with the increase in the pre-strain value, except for the Ti-6Al-4V specimen with 9% pre-strain, there was an increase in tensile strength from 971.53 MPa. to 1037.86 MPa. Furthermore, the pre-strain treatment also did not significantly affect the modulus of elasticity of the test specimen. Only one specimen variation had a significant effect, namely the CP-Ti with a pre-strain of 15%, resulting in Young's modulus of 16.45 GPa.