Introduction: Calcium silicate-based cements has been shown to have improved antibacterial properties when incorporated into the triple antibiotic paste (TAP). However, the new material combination must withstand the tissue environment and be dimensionally stable when employed for endodontic applications. Therefore, this study aims to determine the pH and dimensional stability of mineral trioxide aggregate (MTA) and Biodentine incorporated with TAP. Materials and Methods: A total of 80 cylindrical discs of 6 mm × 3 mm dimensions (n = 20) were prepared with MTA, MTA + TAP (1:1), Biodentine, and Biodentine + TAP (1:1) in Groups 1, 2, 3, and 4, respectively. Each group’s specimens had half of their samples tested for dimensional stability (n = 10) and pH (n = 10). Samples were submerged for 1 min in containers containing 10 ml of distilled water and the initial pH was recorded and after the 7th day using a digital pH meter. To evaluate the dimensional stability, the samples were wrapped in wet gauze and kept at 37°C in the incubator for 24 h. Then, their initial lengths were measured, and were stored in distilled water at 37°C for a month before being measured once more with digital calipers. The data were statistically analyzed using one-way ANOVA, post hoc Tukey, and a paired Student “t” test (P ≤ 0.05). Results: MTA and Biodentine without TAP demonstrated a higher pH than with TAP; nonetheless, at both time points, all groups had an alkaline pH. With the exception of MTA + TAP, all the groups were dimensionally stable at both time intervals, but no significant difference was identified between the groups (P ≤ 0.05). Conclusion: Both MTA and Biodentine combined with TAP exhibited alkaline pH throughout the study period; however, Biodentine combined with TAP was dimensionally more stable compared to MTA with TAP.