This in vitro study was conducted to evaluate effect of surface treatment of zirconia and two resin cements on retentive force of zirconia crowns. Materials and Methods: Forty zirconia crowns (Amann Girrbach AG, Austria) were fabricated and divided into 2 groups according to type of resin cement, group (1) 1 Rely x ultimate clicker (3M Deutschland, Germany) and group (2) Rely x unicem (3M ESPE, USA), each group was then subdivided into 4 groups according to type of surface treatment, no surface treatment, sandblasting, sandblasting with silane and sand blasting with MDP. After cementation retention was measured by Materials Testing Machine (Instron Industrial Products, Norwood, USA) with a load cell of 5 kN. Data were recorded using computer software (Bluehill Lite; Instron Instruments). Results: Group (2) showed higher significant mean of retentive force than group (1). Self-adhesive resin cement showed higher mean of retention (82.72 ± 1 6.91) and (128.21 ± 19.88), compared to conventional (43.86 ± 5.89) and (92.95 ± 5.70), the difference was statistically significant. Sandblasting with MDP showed higher mean of retention (153.88 ± 12.07) and (166.19 ± 12.66), compared to group with no surface treatment (43.86 ± 5.89) and (82.72 ± 6.91) and the difference was statistically significant. Conclusions: Group (1) Rely x ultimate clicker resin cement (conventional resin cement) showed less mean of retentive force than group (2) Rely x unicem resin cement (self-adhesive).