Introduction:. Boswellic acid (BA) is a recently introduced antibacterial agent against root canal infections; however, it is yet unclear how this agent would affect the microhardness of root dentine. Therefore, this study's objective was to compare the effects of using boswellic acid as an intracanal medicament (ICM) with the regularly used one, calcium hydroxide (Ca(OH)2) in terms of the microhardness of root dentine. Material and methods: Sixty single-rooted teeth were sectioned at the cemento-enamel junction (CEJ) level and root canals were prepared till apical size of #30. The prepared teeth were allocated into three groups (n=20): control group, Ca(OH)₂ group and Boswellic acid group. After seven days, medicaments were removed using standardized volume of irrigation. All teeth underwent longitudinal sectioning in a bucco-lingual plane and were embedded horizontally in auto-polymerizing acrylic resin with their dentine surface exposed. Microhardness assessment was performed using Vickers microhardness tester with magnification of 100× and a load of 25 g for 10 second. Results: Both control and Boswellic acid groups "at the coronal and middle sections" showed significantly greater microhardness compared to Ca(OH)2 group (P <0.05), with no significant difference between them. At the apical third, no significant difference (P <0.05) was recorded between the three groups regarding microhrdness. Conclusion: Under the limitations of the current study, Boswellic acid didn't reduce the root dentine microhardness in comparison with Ca(OH)2 when used as ICM.