Objective: To evaluate the influence of different conditioning methods of prepared teeth on the retention of cast metal copings bonded with two self-adhesive resin cements. Method and Materials: Mandibular first molars (n = 80) were prepared to receive metal copings. Sixteen molars were stored in water without interim copings as a control group (CG), while 64 molars were covered with interim copings. Eighty cast copings were laboratory fabricated from Ni-Cr alloy. Interim copings were removed, and 64 molars were cleaned and divided into four groups (n = 16) according to pretreatment methods of prepared molars: no pretreatment (T-NT) and conditioning with self-etching adhesive (T-SE), polyacrylic acid (T-PA), or ethylenediaminetetraacetic acid (EDTA) (T-ED). Each group was further subdivided into two subgroups (n = 8) according to luting cements. RelyX Unicem and seT self-adhesive resin cements were used for cementation of copings. Specimens were stored in water at 37°C for 6 months and then cyclically loaded and thermal cycled. Retentive stress in N was recorded for each specimen. Statistical analyses were conducted with two- and one-way ANOVA and Tukey HSD test. Results: Retentive stress ranged from 526.7 to 692.9 N for RelyX Unicem and 339.8 to 492.3 N for seT. There were no statistically significant differences between the mean retentive stress of the CG, T-SE, and T-PA groups (P > .05). The mean retentive stress of group CG was significantly higher than mean retentive stress of groups T-NT and T-ED (P .05). The mean retentive stress of the control and test groups bonded with RelyX Unicem was significantly higher than the mean retentive stress of the same groups bonded with seT. Conclusion: Conditioning of prepared teeth using polyacrylic acid or self-etching adhesive significantly increased the retentive stress of cast metal copings. Keywords: conditioning method, crowns, luting cements, retention