The study is focused on the mechanical behavior and finite element method (FEM) modeling of glued timber dowel connections with slotted-in steel plates. Standard tests accompanied by a physical optics investigation method were used in order to obtain information about the mechanical properties and stress-strain behavior of glued timber dowel connections with slotted-in steel plates. As such a methodology provides information on the stress-strain state over the surface of a connection, it was used as a verification criterion for a 3D finite-element model. Small-scale glued timber dowel connections with slotted-in steel plates were tested in parallel-to-grain tension to investigate their load-carrying capacity and the load-slip performance of the connection. A three-dimensional finite-element model of the glued timber dowel connections with slotted-in steel plates was developed using existing FE software and verified using the holographic interferograms obtained during step-by-step loading as well as the test results.