Rainfall has become a main trigger of slope failure for embankments in most coastal areas in China. The microbially induced carbonate precipitation (MICP) technique has great potential to improve soil strength and slope stability. In this study, three small-scale biotreated sand embankments and one untreated embankment were first prepared using the injection method. Rainfall scouring tests were then conducted to investigate the slope failure of the embankments. Experimental results revealed that scouring/erosion resistance of biotreated sand embankments was significantly improved comparing to that of the untreated one. The failure time of the embankment increased as the treatment cycles increased. The failure mode of the untreated embankment was the general shear failure, whereas the failure was most likely to occur at shallow depth in biotreated embankments. Using the finite element method (FEM), flow analysis was conducted to simulate the rainfall infiltration in sand embankments and study the effect of biotreatment on the infiltration process. The simulation results were found to be consistent with the experimental results. This study preliminarily investigates the effectiveness of using the MICP technique to prevent slope failure of sand embankments. Considering the complicated environmental factors, more effort towards optimization is still needed for field implementation in the future.