In this work, a novel simulation tool named one-dimensional multijunction solar cell simulator (MSCS-1D) has been reported. This tool provides an easy platform to verify whether the intended work on a multijunction solar cell can be simulated as per expectations. A modified version of spectral p-n junction model has been used to develop this simulator. The congenial dialog box and graphical user interface (GUI) facilitate rapid data entry and visualization of the simulated results. To ascertain the performance of MSCS-1D, the simulated results from this tool were compared with MATLAB simulated results and found in good agreement. The newly developed simulator could provide the user with an easy and fast-run operating procedure compared to the complex MATLAB programming as well as other solar cell simulators available in the literature.