The effect of 1-methylcyclopropene (1-MCP) treatment on the senescence of harvested ‘Younai’ (Prunus salicina Lindl. cv. Younai) plums and its relation to energy metabolism was investigated in this study. Harvested ‘Younai’ plums were treated with 0 (control) and 1.2 μL/L 1-MCP for 12 h, and stored at 25 ± 1 ℃. The cell membrane permeability, ATP, ADP, and AMP content, NAD kinase (NADK) activity, and NAD, NADH, NADP, and NADPH expression was analyzed in the control and sample plums during storage. The results of these analyses revealed that MCP-1 treatment slowed the increase in cell membrane permeability, promoted ATP accumulation during the late stage of fruit storage (12~18 days), and delayed the decrease in the level of energy charge during the whole storage period (compared to the control samples). In addition, 1-MCP treatment resulted in the maintenance of a relatively high NADK activity, a reduction in NAD and NADH content, and an increase in the NADP and NADPH content in the 1-MCP treated-‘Younai’ plums. Based on these results, it was concluded that the MCP-1 treatmentinduced the maintenance of the integrity of the cell membrane structure, and the delay in the senescence of harvested ‘Younai’ plums was correlated with the maintenance of a higher level of energy charge.