Purpose: The purpose of the current study was to evaluate the effect of poly amidoamine dendrimer pretreatment alone and with Nanohydroxy apatite containing adhesive on the integrity of resin dentin bond as affected by PH Cycling . Materials and Methods: A total of eighty dentin samples were divided into four main (A) groups according to the material used where in (A1) group: (PAMAM –NH2) alone, (A2) group: HA containing adhesive alone,(A3) group :Combination of (PAMAM-NH2 +HA adhesive),(A4) group: The control adhesive alone .And each of (A) groups were further subdivided into two (B) groups according to PH Cycling where (B1) exposed to PH Cycling while (B2) not exposed. After (21 days) the shear bond strength of the specimens was measured and the samples were examined by(ESM).Results: For both (B1) and (B2),the results revealed that the highest mean value was recorded in (A3B1) and (A3B2) group while the lowest mean value was recorded in (A4B1)and (A4B2). Conclusion: All the treatment materials used were effective in improving the bond strength and the PH Condition has a significant role in the efficacy of different materials in increasing the bond strength.