This study aimed to evaluate the coronal microleakage of different thickness of different restorative materials (glass ionomer cement (GIC, GC Gold Label 2), composite restoration (SDR, Dentsply Sirona) and (Filtek Z350 XT, 3M ESPE)) used as final restoration in endodontically treated teeth. 72 sound maxillary incisors were used. Following instrumentation, all canals were obturated with gutta-percha (Dentsply Maillefer) and Roth sealer (Roth International Ltd). After 2mm of gutta-percha removal below cemento-enamel junction, the crown was cut until length of 6mm from the gutta-percha to the incisal edge was achieved. The teeth were divided into four experimental groups (n=18) and access restorations were placed in different thickness combinations. Group 1 (G1): 2mm SDR + 4mm Filtek; Group 2 (G2): 4mm SDR + 2mm Filtek; Group 3 (G3): 2mm GIC + 2mm SDR + 2mm Filtek; Group 4 G4): 6mm SDR. All samples were thermocycled (500 thermal cycles between 5o and 55o C and dwell time of 30s), coated with nail varnish leaving 1mm margin around the filling material, immersed in 2% Rhodamine B solution and sectioned longitudinally. The dye penetration was observed under a stereomicroscope (Olympus SZX7) with 1.25x magnification. The data were analysed using Kolmogorov-Smirnov test, ANOVA test and post-hoc Tukey’s HSD test. There was significant difference of microleakage among all groups. G1 showed least microleakage but with no significant difference between G1 and G3 (p=0.513) and G1 and G4 (p=0.477). G2 showed significant microleakage compared to G1, G3 and G4 (p