The relationship of vitamin C content with water state and ice crystals of mango was investigated under different state/phase transitions (temperature fluctuations) during frozen storage. The temperature of frozen mango was modulated from −65 °C for different states, namely, rubbery (T > Tm′), partially freeze-concentrated (Tg′′ < T < Tm′) and glassy states (T < Tg′ and Tg′ < T < Tg″). The results revealed that in the glassy state, frozen mangoes had less water mobility, freezable water, and smaller ice crystals, resulting in higher vitamin C compared with samples under other conditions. The vitamin C content continued to decrease during frozen storage even in the glassy state without temperature fluctuations. Furthermore, there was a significant decrease in the vitamin C content in frozen mangoes subjected to temperature fluctuations above Tg″ and Tm′, depending on the water mobility, amount of freezable water and size of ice crystals over time.