Objective To investigate the dynamic changes in serum microRNA-15b (miR-15b) and vascular endothelial growth factor (VEGF) in preterm infants with mild or moderate-to-severe bronchopulmonary dysplasia (BPD), as well as their value in assessing short-term neurodevelopment. Methods A retrospective analysis was conducted on the medical data of 156 preterm infants with BPD who were admitted to the neonatal intensive care unit from January 2020 to February 2023. According to the severity of BPD, they were divided into a mild group (n=88) and a moderate-to-severe group (n=68). Serum levels of miR-15b and VEGF were measured on postnatal days 1, 7, 14, and 28. Repeated measures analysis of variance was used to assess the dynamic changes in serum levels of miR-15b and VEGF. The mediating effect of VEGF between miR-15b and short-term neurological development was tested and analyzed using the stepwise regression method and the Bootstrap method. Logistic regression analysis was used to identify factors influencing adverse neurodevelopmental outcomes. Results In the mild group, there was a significant reduction in the serum level of miR-15b and a significant increase in VEGF over time (P<0.05), while in the moderate-to-severe group, there was a significant increase in miR-15b and a significant reduction in VEGF over time (P<0.05). Serum miR-15b and VEGF levels were important factors influencing neurodevelopmental outcomes, showing independent correlations (P<0.001). The mediating effect analysis indicated that miR-15b indirectly affected short-term neurodevelopment by inhibiting VEGF expression [indirect effect: -0.705 (95%CI: -1.178 to -0.372)], with the indirect effect accounting for 54.36% of the total effect. Conclusions There are different changing trends in serum levels of miR-15b and VEGF in preterm infants with mild and moderate-to-severe BPD. miR-15b primarily influences neurodevelopment through VEGF.