Bronchopulmonary dysplasia (BPD) is a multifactorial chronic lung disease of premature infants. BPD can be attributed to the dysregulation of normal lung development due to ventilation and oxygen toxicity, resulting in pathologic complications of impaired alveolarization and vascularization. MicroRNAs (miRNA) are small noncoding RNAs that regulate gene expression posttranscriptionally and are implicated in diverse biological processes and diseases. The objectives of this study are to identify the changed miRNAs and their target genes in neonatal rat lungs in response to hyperoxia exposure. Using miRNA microarray and real-time PCR analyses, we found downregulation of five miRNAs, miR-342, miR-335, miR-150, miR-126*, and miR-151*, and upregulation of two miRNAs, miR-21 and miR-34a. Some of these miRNAs had the highest expression during embryonic and early postnatal development. DNA microarray analysis yielded several genes with conserved binding sites for these altered miRNAs. Glycoprotein nonmetastatic melanoma protein b (GPNMB) was experimentally verified as a target of miR-150. In summary, we identified seven miRNAs that were changed in hyperoxia-exposed neonatal lungs. These results provide a basis for deciphering the mechanisms involved in the spatial and temporal regulation of proteins that contribute to the pathogenesis of BPD.