The electrocardiogram (ECG) continues to remain a crucial investigation in cardiology even after a century of its discovery despite so much sophisticated investigations today. It not only gives the diagnosis but also gives other crucial information such as prognosis, management plan and result of the treatment in many cardiac diseases. But it should be realised that the ECG also gives almost so much information in many non-cardiac situations. This article explores the role of ECG in so many non-cardiac conditions such as Lung diseases, Gastrointestinal diseases, Neurological illnesses, Electrolyte abnormalities and poisoning. Just a change in posture and skeletal abnormalities can also alter ECG to mimic a cardiac disease. In each of these conditions ECG changes are explained with representative ECGs and its importance in managing that particular non-cardiac condition is also discussed.