Nuclear factor of activated T cells 5 (NFAT5) is a transcription factor that can be activated by extracellular tonicity. It has been reported that NFAT5 may increase the transcription of certain osmoprotective genes in the renal system, and the aim of the current study was to explore the role of NFAT5 in seawater inhalation‑induced acute lung injury. Though establishing the model of seawater inhalation‑induced acute lung injury, it was demonstrated that seawater inhalation enhanced the transcription and protein expression of NFAT5 (evaluated by reverse transcription‑polymerase chain reaction, immunohistochemistry stain and western blotting) and activation of nuclear factor (NF)‑κB (evaluated by western blotting and mRNA expression levels of three NF‑κB‑dependent genes) both in lung tissue and rat alveolar macrophage cells (NR8383 cells). When expression of NFAT5 was reduced in NR8383 cells using an siRNA targeted to NFAT5, the phosphorylation of NF‑κB and transcription of NF‑κB‑dependent genes were significantly reduced. In addition, the elevated content of certain inflammatory cytokines [tumor necrosis factor α, interleukin (IL)‑1 and IL‑8] were markedly reduced. In conclusion, NFAT5 serves an important pathophysiological role in seawater inhalation‑induced acute lung injury by modulating NF‑κB activity, and these data suggest that NFAT5 may be a promising therapeutic target.