To compare long-term outcomes of mechanical versus bioprosthetic aortic valve replacement (AVR) in patients under the age of 50, we performed a study-level meta-analysis with reconstructed time-to-event data including studies published by December of 2023. The primary outcome was overall survival. Secondary outcomes included reoperation, major bleeding, and stroke. Five studies met our inclusion criteria with a total of 4245 patients (2311 mechanical, 1934 bioprosthetic). All studies were observational and the mean age of groups across the studies ranged from 38.2 to 43.0 years. The median follow-up time was 11.4 years (IQR, 6.9-15.0). Bioprosthetic AVR was associated with reduced overall survival and higher risk of all-cause death (HR, 1.170 [95% CI, 1.002-1.364], P=0.046), increased risk of reoperation over time (HR, 2.581, [95% CI, 2.102-3.168], P<0.001), decreased risk of major bleeding (HR, 0.500, [95% CI, 0.367-0.682], P<0.001), and decreased risk of stroke (HR, 0.751, [95% CI, 0.565-0.998], P=0.049) compared to mechanical AVR in patients under 50. In conclusion, for patients under the age of 50, bioprosthetic AVR is associated with increased mortality and risk of reoperation compared to mechanical valves. On the other hand, mechanical AVR is associated with an increased risk of major bleeding events and stroke. These aspects should be carefully considered during the selection of valve type in this age group; however, we should keep in mind that the statistically significant differences in the risk of all-cause death and stroke might not be clinically relevant (due to marginal statistical significance).