This study was conducted to observe the effect of formalin application on the post-harvest quality and shelf life of mango. Mango samples were treated with different concentrations of formalin solutions (10, 100 and 1000 mg/L) in two different modes (dipping and spraying) and stored for seven days at ambient condition. Physical characteristics, such as weight loss, color, texture and shrinkage and residual formalin content were observed at every alternate day during storage period. Formalin treatment (dipping and spraying) did not bring up any positive effect in increasing the shelf life of mango. Rather treated with higher concentration of formalin solution (10<100<1000 mg/L) caused internal and external deterioration which is explained in discussions section. Residual formalin content of mangoes for the both treatments decreased readily according to the treatment mode. The overall study indicates that the post-harvest quality and shelf life of mango could not be improved treating with any concentration of formalin either spraying or dipping mode.