Selective Laser Sintering (SLS) 3D printing is an emerging technology being gradually adapted in the automotive and aerospace industry. Especially, automotive companies utilize the SLS 3D printing to produce design prototypes and test products in their design and development processes. While the failures of 3D printed products have sometimes been reported in the field, there are a limited number of reliability studies on the 3D printing applications. In this research, thus, we aim to assess the thermal mechanical reliability of 3D printed products in order to verify the feasibility of the 3D printing technology into industrial applications. In the experiments, several samples with multiple dimensional features are exposed to high temperatures and high moisture levels to evaluate the dimensional stability under accelerated stress conditions. The results will confirm the feasibility and applicability of the 3D printing technology, and are expected to provide a basis of systematic reliability evaluation framework for 3D printed products.