BACKGROUND Endodontically treated teeth often lack sufficient support for a permanent restoration. During post space preparation, it is important not to disturb the integrity of the apical seal. OBJECTIVE This study compared the effect of immediate versus delayed post space preparation on the apical seal using four different sealers. METHODS One hundred and thirty single rooted teeth were biomechanically prepared and obturated with single cone gutta-percha and 4 sealers: Endoflas FS, AH Plus, Gutta flow and MTA. Teeth were divided randomly into eight groups, post spaces were prepared using Gates Glidden drills immediately for group I, III, IV and VII. For groups II, IV, VI and VIII prepared after storage of the specimens in 100% humidity for one week. The samples were kept in methylene blue dye, centrifuged at 3000 rpm for 3 min sectioned and then measured under stereomicroscope for apical leakage. METHODS The data was analysed using one way ANOVA and post hoc Tukey test. RESULTS All the specimens showed dye leakage, and a statistically significant difference was seen among all the groups (P > 0.05) except Gutta flow. CONCLUSIONS Less leakage is seen when post space is prepared immediately.