Electrospinning is an easy and efficient method for preparing nanofibers on laboratory and industrial scales. In recent years, various studies have been done with special attentions to specific structures, increasing the application and eliminating the shortcomings of previous methods. Janus structure is one of the new and widely used structures that due to the limitations and challenges in achieving this structure, such as nozzle design, phase separation of two polymer solutions during electrospinning, flow rate control, optimal voltage and other parameters, the published reports in this field, are limited. Side-by-side electrospinning is one of the common ways to achieve this special structure. In this method, with appropriate nozzle design, two polymer solutions can be electrospun simultaneously. In addition, the nozzle design and the related parameters such as needle diameter, angle, and distance between the nozzles are of special importance. Also, parameters related to the rheological behavior of the polymer, especially viscosity, are crucial in achieving this particular structure. In this paper, the methods of preparation of Janus nanofibers by side-by-side electrospinning method, new structures based on these nanofibers, including the study of structure and production methods through side-by-side electrospinning, are briefly reviewed.