Introduction: Obturation of the root canal system is an integral part of endodontic treatment. The main objective of obturation is to three dimensionally fill the root canal, to provide adequate seal and prevent leakage from periapical tissues. For root canal sealers to achieve these objectives, it must exhibit adequate physical properties Aim: the present study evaluated the effect of adding different percentages of calcium hydroxide nano particles (CHNPs) to a calcium hydroxide-based sealer (Sealapex) on the physical properties and comparing it to the unmodified formula of the sealer. Materials and methods: Calcium hydroxide nanoparticles were added to (Sealapex) root canal sealer in the concentrations of 3% and 8% by weight respectively. Samples were divided into three main groups: Group I (Sealapex+3%CHNP), Group II (Sealapex+8%CHNP) and Group III (Sealapex) in the conventional formula. Setting time and flow were assessed according to ISO standardization 6878:2012 specification. Wettability was assessed using Contact angle goniometer. Data showed parametric distribution and were analyzed using one-way ANOVA followed by Tukey's post hoc test for intergroup comparisons and repeated measures ANOVA followed by Bonferroni post hoc test for intragroup comparisons. Results: There was a significant increase in setting time for Group I (Sealapex+3%CHNP), on the other hand, group II (sealapex+8%CHNP) showed significant decrease in setting time. Regarding the flow of sealers there was a significant increase in flow for both Group I (Sealapex+3%CHNP) and Group II(Sealapex+8%CHNP) in comparison to the conventional formula. Conclusion: addition of calcium hydroxide nanoparticles (CHNP) enhanced physical properties of root canal sealer Sealapex.