Flow regulation between two tandem circular cylinders is a key topic in a variety of engineering applications. The numerical study of laminar flow regimes over two tandem grooved cylinders is presented in this research. Both cylinders have an identical diameter D, and separated by a distance L= 4D. The upstream cylinder has a single square groove whereas the downstream cylinder has a smooth surface. The investigations were conducted at different Reynolds number, Re≤ 200, and groove orientation (0°, 45°, and 90°) measured from the stagnation point. The effects of Reynolds number and groove position on the leading surface of the cylinder are investigated. While the lift coefficients of tandem grooved cylinders can be enhanced by up to 45% when compared to tandem smooth cylinders, the drag coefficients of tandem grooved cylinders are around 20% lower. Furthermore, considerable changes in the upstream wake is detected due to the presence of the groove on the upstream cylinder. It is also found that once the groove is set at 45° and 90° for the upstream cylinder, the downstream cylinder experiences a maximum and minimum peaks of pressure coefficient, respectively.