To determine mechanical properties or other relevant parameters of plastic materials, devices such as tensile testing machines are widely used. However, these procedures are performed with relatively expensive equipment that is not easily available in educational institutions or companies. For this reason, the following work presents the development and validation of a cost-effective machine capable of performing tensile tests with uniaxial loads on plastic materials. The main characteristics regarding the mechanical, electronic, and software design that have been developed and implemented for the correct operation of the machine are briefly and clearly disclosed. Likewise, the calibration process was performed using a known spring elastic constant. Additionally, the application and validation of the machine were carried out by comparing tensile tests done on the plastic straps with tests done in another machine. The results obtained by the developed machine are similar to those estimated by the validation machine in terms of mass and strain, obtaining an average accuracy of 2.46% and 2.17%, respectively. Finally, the machine sale price was estimated at $1,908 USD, a reduction cost of 68.2% compared with other similar machines in the industry.