Purpose: This study was conducted to evaluate apical leakage of post space preparation when performed at different time intervals immediately after root canal obturation (after setting of the sealer used) or delayed after two weeks. Materials and methods: Forty-five extracted human anterior single rooted teeth were selected and placed in sterile physiologic saline solutions. Teeth were decoronated perpendicular to their long axis and 2mm above the cemento-enamel junction (CEJ). The canals were filed to mater apical file size #40 using step-back tech. The root canals were enlarged and flared to size #55. The specimens were divided randomly into 3 equal groups(15 samples each) , according to type of sealer that used during root canal treatment group (1) Eugenol-based sealer, group(2) Calcium hydroxide-based sealer and group (3) Resin –based sealer, After root canal obturation, the specimens were further subdivided into three subgroups (5 samples each): subgroup (A) without post space preparation as control, Subgroup (B) with immediate post space preparation and Subgroup (C) with delayed post space preparation. Results: Calcium hydroxide based sealer group recorded the highest mean value of apical leakage followed by Zinc oxide eugenol-based sealer and AD SEAL resin based sealer which recorded the lowest mean value with no statistical significant difference (P˃0.05). Regarding the effect of time interval control sub group recorded the statistically significant lowest mean value followed by immediate subgroup, while delayed subgroup recorded the statistically significant highest mean value (P ˂0.05). Conclusions: The type of sealer had major effect on the apical seal of endodontically treated teeth. Post-space preparation affects the apical seal of endodontically treated teeth. The effect of immediate preparation on apical seal was significantly lesser than delayed post space preparation.