To elucidate the potential biological functions of long non-coding RNA (lncRNA) MIAT in the development of hypoxic pulmonary hypertension (HPH) and the underlying mechanism. Twenty Sprague Dawley (SD) rats were randomly assigned into normoxia group (n=10) and hypoxia group (n=10), respectively. In vivo HPH model in rats was established by hypoxic induction. Expression levels of MIAT and miR-29a-5p in rats were detected. Meanwhile, hemodynamic indicators in rats were examined. In vitro HPH model was conducted in hypoxia-induced HPAECs. The interaction between MIAT and miR-29a-5p was assessed by Dual-Luciferase reporter assay. Moreover, their regulatory effects on viability, migratory ability, oxidative stress, and the Nrf2 pathway in hypoxia-induced HPAECs were examined. MIAT was upregulated in both in vivo and in vitro HPH models, while miR-29a-5p was downregulated. Knockdown of MIAT suppressed viability, migratory ability, and oxidative stress in hypoxia-induced HPAECs. MiR-29a-5p was the target gene binding MIAT, and silence of miR-29a-5p partially relieved the inhibitory effects of MIAT on the above regulations in HPAECs. MIAT promotes proliferative and migratory abilities, as well as oxidative stress in hypoxia-induced HPAECs by targeting miR-29a-5p, thus aggravating the development of HPH.