The aim of this study was to evaluate the influence of n-butyl cyanoacrylate (NBCA) coating of freshly mixed mineral trioxide aggregate (MTA) on its microhardness after setting under conditions of moisture and human blood exposure. MicroMega MM-MTA samples were prepared using Teflon molds (6 mm × 4 mm). Four experimental groups (n = 4) were established: control (MTA + phosphate-buffered saline (PBS)), MTA coated with NBCA (PeriAcryl) + PBS, MTA + blood + PBS, and MTA coated with NBCA + blood + PBS. Samples assigned to the blood-exposure groups were exposed to human blood for 15 min, rinsed, and subsequently stored in PBS. Prior to microhardness testing, all samples were incubated in PBS for seven days. Microhardness was measured using a Vickers microhardness tester, with five indentations performed on each specimen (20 measurements per group). Data were analyzed using the Shapiro–Wilk test for normality, Levene’s test, and two-way ANOVA, followed by Tukey’s post hoc test. The analysis revealed significant differences among the experimental groups (p < 0.001). Post hoc analysis demonstrated statistically significant differences between tissue glue-coated and uncoated samples (p < 0.05). Within the limitations of this in vitro study, coating MTA with NBCA tissue glue during the setting period significantly increased its microhardness following exposure to human blood and PBS.