Statement of the problem: The misfit of fiber post to noncircular or flared root canal can result in the reduction of the fiber post retention.Aim: to evaluate retention of Macro-Lock and smooth fiber posts with and without relining of the posts with composite resin when restoringendodontically treated single rooted teeth with flared canals.Materials and methods: Forty eight human mandibular premolars were elected for this study. The crowns were removed 2 mm coronal to the cement-enamel junction and the root canals were endodontically treated and flared at 10 mm for the post spaces. The samples were randomly allocated into four groups (n=12); MLC: Macro-Lock fiber posts relined with composite resin, ML0: Macro- Lock fiber posts without relining,RXC: RelyX fiber posts relined with composite resin and RX0: RelyX fiber posts without relining. The posts were cemented with self-adhesive resin cement and thermo-cycled for 2000 cycles. Three 1.5-mm transverse thick slabs were obtained per root and identified as cervical, medium and apical thirds and the push-out test was performed at a crosshead speed of 0.5 mm/min until post dislodgement occurred. Three-way analysis of variance ANOVA and Tukey’s post-hoc tests were used to detect significance between the groups.1 Master degree of Fixed Prosthodontics, Cairo University, Egypt2 Professor of Fixed Prosthodontics, Cairo University, Egypt3 Professor of Fixed Prosthodontics, Cairo University, EgyptResults: The results revealed that RXC and ML0 groups recorded significant higher bond strength means value than RX0 and the MLC groups (p<0.05). Whereas no significant difference was found betweenRXC and ML0 in bond strength means value (p>0.05).Conclusion: Relining of fiber post significantly improved the retention of smooth fiber posts, and reduced the retention of macro-retentive fiber posts to flared root canal.