This in vitro investigation compared the shear bond strength (SBS) of four dentin substitute/replacement materials to caries-affected dentin of primary teeth. Dentin surfaces were randomly divided into four groups of 12 each according to the material used as follows: SDR/Smart Dentin Replacement, Biodentine, Multicore Flow, and Fuji II LC. The SBS was measured and failure modes were determined. There was a statistically significant difference in the mean values of SBS among the four materials (F=741.523, p<0.0001). The mean values of SBS of SDR were statistically significantly higher followed by Multicore Flow compared to the other groups. The mean values of the four materials were significantly different from each other in all combinations of pairs of four materials. The SBS between the four dentin substitute/replacement materials to dentin of primary teeth was significantly different. The highest SBS was for SDR followed by Multicore Flow then Fuji II LC and the lowest was for Biodentine.