Vortices forming near the slag-steel interface in the mold can entrap inclusions and cause defects in continuous casting of steel slabs. Lab experiments employing a 1/3rd scale water model were performed to quantify the effects of stopper rod asymmetry on vortex formation. Three stopper-rod placements (aligned, front-misaligned and left-misaligned) were considered. Vortex formation was visualized with a high speed camera by placing sesame-seed tracer on the surface, which enables counting the number and detecting the location of vortices with time. Impeller flow probes were adopted to measure velocity profiles near the surface. Misaligning the stopper-rod placement induces asymmetric flow, resulting in asymmetric surface velocity, velocity variations, and turbulent kinetic energy. These factors influence vortex frequency and location among four zones near the SEN. Most vortices form at the left regions beside the SEN with a left-misaligned stopper-rod. Vortices form more preferentially at outside regions with a front-misaligned stopper-rod.