Polylactic acid (PLA) is increasingly vital in 3D printing due to its sustainability and versatility in applications ranging from product packaging to medical implants. Ensuring its mechanical reliability under load is critical for expanding its industrial use. This study evaluated the mechanical properties of fully loaded samples produced from PLA filament using a 3D printer, through experimental tensile tests and finite element analysis (FEA). The samples were designed in accordance with the ASTM D638 Type I standard and fabricated using a 3D printer. Unlike prior studies, this work uniquely combines the ANSYS Explicit Dynamics module with the Johnson–Cook material model to simulate high-deformation behavior in fully loaded specimens, addressing gaps in the literature regarding comprehensive mechanical analysis of 3D printed PLA. Fracture zones were examined with a digital microscope. Experimental tensile tests on fully loaded PLA samples accurately simulated the stress distribution using FEA. These findings offer insights into optimizing 3D printing parameters to improve interlayer bonding, reduce defects, and enhance PLA’s reliability in industrial applications.