Skeletal muscle atrophy refers to the decline in muscle mass and strength that occurs under various conditions, including aging, starvation, cancer and other cachectic diseases. Muscle atrophy caused by aging, known as sarcopenia, primarily occurs after 50 years of age. Muscle atrophy‑related genes, including atrogin1/muscle atrophy F‑box (MAFbx) and muscle RING finger 1 (MuRF1), are expressed early in the muscle atrophy process, and their expression precedes the loss of muscle mass. The present study investigated the potential anti‑atrophic effects of the Pyropia yezoensis peptide PYP1‑5. The MTS assay did not detect cytotoxic effects of PYP1‑5 on C2C12 mouse myoblast cells. Subsequently, the anti‑atrophic effects of PYP1‑5 on skeletal muscle cells was examined by treating C2C12 myotubes with 100 µM dexamethasone (DEX) and/or 500 ng/ml PYP1‑5 for 24 h. Compared with the control, myotube diameter was reduced in DEX‑treated cells, whereas PYP1‑5 treatment protected against DEX‑induced muscle atrophy. MAFbx and MuRF1 protein and mRNA expression levels were detected by western blot analysis and reverse transcription‑quantitative polymerase chain reaction, respectively. The results demonstrated that PYP1‑5 significantly reduced the expression of atrogin1/MAFbx and MuRF1. Therefore, data from the present study suggest that PYP1‑5 inhibits the expression of atrogin1/MAFbx and MuRF1 in C2C12 cells, and these characteristics may be of value in the development of anti‑atrophy functional foods.