This paper addresses the effect of diagonal placement of expansion ramps on the decay characteristics of a supersonic rectangular jet. The diagonal placements of ramps induce additional vortices near the nozzle exit apart from the corner vortices emanating from the rectangular corners which is further enhances jet decay. A Mach 1.8 rectangular jet issuing from a converging-diverging nozzle of aspect ratio 2 and Reynolds number 1.861×105 is considered for the study. To avoid the losses in divergent section, the shape of cross-section from the throat was maintained rectangular. Numerical simulations and Schlieren image study were carried out to validate the experimental results obtained from total pressure data. Both experimental and numerical studies show that the expansion ramps played a significant role to enhance decay rate. The ramps placed on the minor side caused maximum supersonic core length reduction indicating accelerated decay. This minor side ramps were found to be more effective at over-expansion conditions whereas the major side ramps for under-expansion conditions. Also, both experimental and numerical studies have shown that shock waves are rendered weaker by the minor side placement of ramps at all expansion levels.