Abstract Immersion treatment of a new 1-methylcyclopropene (1-MCP) formulation has shown beneficial effects on post-harvest quality retention of several fruit commodities. We examined the effects of 1-MCP concentration (0.1–10 mg/L) and immersion time (0.5–5 min) on the shelf-life of muskmelon (Cucumis melo L. var. reticulatus L. Naud) fruit. Regardless of ripening stage at harvest or storage temperature, 1-MCP immersion improved the retention of firmness and soluble solids content, while delaying the development of undesirable quality attributes, including overripe skin color, sunken discoloration area, and overripe flavor. The efficiency of 1-MCP increased with increasing concentration and immersion time, although at 10 mg/L, efficiency was maximized with as little as a 30-s immersion. Importantly, no undesirable side-effects were detected. These results suggest that 1-MCP immersion is an effective method for extending the shelf-life of muskmelon fruit. Furthermore, this technique requires only a quick dip, which is desirable for commercial implementation.