Aims of this study were to evaluate in vitro the apical sealing ability of experimental nano hydroxyapatite resin based endodontic sealer and to compare with AH26 sealant material. A total of 76 extracted single rooted human teeth were instrumented using Profile and randomly divided into two groups of 33 teeth respectively. Teeth in the first group was obturated using gutta-percha with AH26. The second group was obturated with the experimental sealer. All teeth were coated with nail polish except 2 mm from foramen apical. The teeth were then suspended in 2% methylene blue for 7 days and sectioned longitudinally for measuring penetration of the dye using stereo-microscope(x36)with Leica Imaging System. Analysis of the results was performed with t-test.The mean penetration of AH26 was 0.44 (0.63) mm and 0.75 (0.81) mm for experimental sealer.The result showed that there was no statistically significant difference (p>0.05) in apical sealing ability between AH26 and experimentalsealer. Experimental sealer provided an adequate apical seal against dye penetration in similar level with AH26 and could be used as an alternative to the commercial available endodontic sealer.