We study transient post-welding shift (PWS) with experiment and simulation. Measurement of PWS with noncontact displacement sensor reveals that a typical laser welding of TO-can pigtail package involves transient PWS with multiple characteristic time scales. Finite element modeling (FEM) of a three-dimensional structure with thermo-mechanical coupling helps us visualize the dynamics of the miniscule PWS. This study gives a better understanding on the physical process of transient PWS.