The effect of the ripening stage and infusion with calcium lactate and sucrose on the quality and microstructure of frozen mango was investigated. Partially ripe and ripe mangoes cubes were infused in 1% calcium lactate solution or a combination of 1% calcium lactate and 50% sucrose solution for 1 h before freezing at −20 °C and stored for 14 days. After thawing, both the partially ripe and ripe mangoes treated with the combination of calcium lactate and sucrose exhibited the highest firmness value, sensory firmness score and lowest drip loss. Light microscope images also illustrated less damage to the cell wall of mango pretreated with calcium and sucrose. The calcium-reinforced structure of the fruit and osmotic dehydration with sucrose reduced the freezable water content and consequently limited ice crystal damage. Furthermore, partially ripe mango was more suitable for freezing than ripe mango due to its stronger cell wall structure.