There is concern that the use of sodium hypochlorite (NaOCl) and RC-Prep may lower the bond strength of resin cements. The objective of this study was to evaluate the effect of 5% NaOCl and RC-Prep treatment on the bond strength of a resin cement, C&B Metabond. Control roots (group 1) were biomechanically prepared using 0.9% NaCl as an irrigant; group 2, roots with 5% NaOCl; group 3, roots with RC-Prep; group 4, roots with 0.9% NaCl followed by 10% ascorbic acid; group 5, roots with 5% NaOCl followed by 10% ascorbic acid (pH 4); group 6, roots with 5% NaOCl followed by 10% neutral sodium ascorbate; and group 7, roots with RC-Prep followed by 10% ascorbic acid. All roots were then filled with C&B Metabond, incubated in water for 24 h, and then cross-sectioned into six 1-mm thick slabs representing cervical and middle root dentin. The slabs were trimmed and tested for tensile bond strength. The results demonstrated that both 5% NaOCl and RC-Prep produced significantly (p < 0.05) large reductions in resin-dentin bond strengths, and the reductions could be completely reversed by the application of either 10% ascorbic acid or 10% sodium ascorbate.