Lung adenocarcinoma (LUAD) is the most common histological subtype of lung cancer. Previous studies have found that many microRNAs (miRNAs), including miRNA‑126‑3p, may play a critical role in the development of LUAD. However, no study of LUAD has researched the synergistic effects and co‑targets of both miRNA‑126‑3p and miRNA‑126‑5p. The present study used real‑time quantitative polymerase chain reaction (RT‑qPCR) to explore the expression values of miRNA‑126‑3p and miRNA‑126‑5p in 101 LUAD and 101 normal lung tissues. Ten relevant microarray datasets were screened to further validate the expression levels of miRNA‑126‑3p and ‑5p in LUAD. Twelve prediction tools were employed to obtain potential targets of miRNA‑126‑3p and miRNA‑126‑5p. The results showed that both miRNA‑126‑3p and ‑5p were expressed significantly lower in LUAD. A significant positive correlation was also present between miRNA‑126‑3p and ‑5p expression in LUAD. In addition, lower expression of miRNA‑126‑3p and ‑5p was indicative of vascular invasion, lymph node metastasis (LNM), and a later tumor/node/metastasis (TNM) stage of LUAD. The authors obtained 167 targets of miRNA‑126‑3p and 212 targets of miRNA‑126‑5p; 44 targets were co‑targets of both. Eight co‑target genes (IGF2BP1, TRPM8, DUSP4, SOX11, PLOD2, LIN28A, LIN28B and SLC7A11) were initially identified as key genes in LUAD. The results of the present study indicated that the co‑regulation of miRNA‑126‑3p and miRNA‑126‑5p plays a key role in the development of LUAD, which also suggests a fail‑proof mode between miRNA‑3p and miRNA‑126‑5p.