Abstract : Aluminum phosphide (ALP) is a common self-poisoning agent in Egypt due to its low price and easy availability and High mortality of ALP toxicity is mainly attributed to cardiovascular collapse. Unfortunately, there is no specific antidote to manage the cardiotoxic effects of ALP. To evaluate the protective effect of melatonin on the cardiotoxicity induced in cases of acute ALP poisoning. Sixty cases with acute ALP poisoning were allocated into two groups. The first group received the standard supportive treatment plus melatonin, whereas the second group received the standard supportive treatment only. The most prominent ECG abnormality in two groups was sinus tachycardia (56.7% and 40 % respectively). Troponin I level is within normal reference range in first group but it had been increased in the second group with a significant difference in the median troponin I level between both groups (0.13 versus 0.22 respectively). Melatonin use in acute ALP poisoning seem to have shortened the length of hospital stay. besides, it stabilizes Troponin I level within the normal reference range.