This study investigates the electronic properties of a single layer of the novel Janus material GeSnS using density functional theory. By utilizing the hybrid functional HSE06 in addition to the standard PBE approximation, the study aims to obtain accurate findings about how changes in strain and electric field affect the material's electronic properties. The results of the study reveal that the natural energy bandgap of the GeSnS monolayer is 2.2 eV and that it exhibits an indirect band gap behavior. The study also shows that by applying strain or an electric field, the bandgap of the material can be changed, which has significant implications for the material's potential applications. The study found that when strain is applied, the bandgap changes significantly, and a band shift occurs under certain conditions. The band gap energy increases with tensile strain while decreasing with a compressive one. Furthermore, the study discovered that the electric field has a slight effect in changing the bandgap of GeSnS monolayer when the electric field is changed from 0 to 8 V/ang. These findings suggest that GeSnS could be a promising material for applications such as solar cells and optoelectronics, where the bandgap needs to be adjusted for optimal performance. The ability to tune the bandgap of the material through strain or electric field could also be beneficial in other fields such as electronics, spintronics, and quantum computing. The study provides valuable insight into the potential of GeSnS and opens the door for further research in this field.