The aim of the present study was to investigate whether necroptosis occurs in high glucose (HG)-induced H9c2 cardiac cell injury and whether the activation of aldehyde dehydrogenase 2 (ALDH2) can inhibit necroptosis. H9c2 cardiac cells were treated with 35 mM glucose to establish a HG‑induced cell injury model. Alda‑1 (20 µM), a specific activator of ALDH2 and necrostatin‑1 (Nec‑1, 100 µM), an inhibitor of necroptosis were used to treat H9c2 cardiac cells under HG conditions. Cell viability was measured using a Cell Counting Kit‑8 assay and reactive oxygen species (ROS) generation was measured by the dihydroethidium staining method. ALDH2 activity was measured at 450 nm. The mRNA and protein expression of ALDH2, necroptosis‑associated genes, receptor‑interacting protein (RIP)1, RIP3 and mixed lineage kinase domain like pseudokinase (MLKL), were analyzed by reverse transcription‑quantitative polymerase chain reaction and western blotting. The expression of cleaved caspase‑3 protein was also examined by western blotting. The results demonstrated that under HG conditions, cell viability, ALDH2 activity, mRNA and protein expression were decreased. Furthermore, ROS generation, mRNA and protein expression of RIP1, RIP3, MLKL and the protein expression of cleaved caspase‑3 were increased. Treatment with Alda‑1 or Nec‑1 attenuated HG‑induced downregulation of ALDH2 activity, mRNA and protein expression. In addition, RIP1, RIP3, MLKL mRNA, and protein expression were downregulated. Furthermore, Alda‑1 but not Nec‑1 decreased cleaved caspase‑3 protein expression. Collectively these data indicated that activation of ALDH2 protected H9c2 cardiac cells against HG‑induced injury, partly by inhibiting the occurrence of necroptosis.