The most commonly used core material for root canal filling is gutta-percha and as the gutta-percha by itself cannot obturate the complete root canal system, owing to its poor sealing properties hence, a sealer is used in combination with root filling material. Sealer is more important than the core obturating material. Sealer plays a secondary role by merely reinforcing (binding or luting) the gutta-percha to the canal walls, however, it is now confirmed that the sealer has a prime role in sealing the canal by blocking the irregularities between the canal space and the core filling material. To investigate the effectiveness of the apical seal obtained by different sealers used in conjugation with cold lateral condensation technique of obturation using gutta-percha under stereomicroscope. One hundred single-rooted extracted human permanent teeth with a single root canal were used in this in-vitro study. The sealers tested were conventional Zinc oxide eugenol sealer, Apexit, AH-Plus and Roekoseal Automix (RSA). The specimens were examined under a stereomicroscope. For the analysis of data Snedocor's F test for the quality of variances among the experimental group and control group (One-Way ANOVA) were employed. The polydimethylsiloxane endodontic root canal sealer RSA provided a significantly better apical seal followed by AH plus and Apexit whereas conventional zinc oxide eugenol showed the lowest sealing ability. It was concluded that there were statistically significant differences amongst the experimental groups. The shrinkage related to setting and potential dissolution might risk the proper seal of the root canal leading to treatment failure.