The aim of this study was to compare the efficacy of silane and a novel bioinspired polydopamine functionalization on the adhesion strength of glass fiber posts cemented to root dentin. Sixty-four surface treated posts [polydopamine (group 1 = 32) or silane (group 2 = 32)] were cemented in root canals of 64 extracted and decoronated mandibular premolars by using 3 commercial brands of self-adhesive resin cements (subgroups A, B and C) or a total-etch resin cement (subgroup D). The samples were subjected to push-out bond strength testing at 24 h and at 6 months after storage in water. Each sample was subdivided into six slices (three slices of the coronal and three slices of the apical) to determine the push-out bond strength in the coronal and apical third. The mean bonding strength value of the 3 slices both for the coronal and apical third was calculated as megapascals (MPa) and the data were statistically analyzed using post hoc Tukey HSD and Student t tests using four-way ANOVA (P = 0.05). Failure modes were investigated using scanning electron microscopy (SEM). The number of adhesive failures at the dentin-cement interface dropped when polydopamine was used (12–33%). Failure between the post and cement interface also dropped (4–13%) in all the resin cement groups, except the Subgroup C (17%). Polydopamine treatment significantly increased the adhesion strength for all cements compared to silanization at 24 h (P < 0.05), however at 6 months, only for the self-adhesive cements (P < 0.05). Polydopamine surface treatment improves the short-term bond strength of fiber-posts cemented to root canal dentin. The positive effect of polydopamine on long-term bond strength did not appear to be significant for the total-etch resin cement.