The early diagnosis of any disease has the potential to save the life of a patient. Over the decades, electrocardiogram (ECG) signals have been widely used for the diagnosis of various cardiovascular diseases. This may be attributed to the ability of the ECG signals to divulge information about the cardiac electrophysiology in a noninvasive manner. Although various methods have been reported by researchers for the processing of the ECG signals in the last few decades, the wavelet transform-based joint time-frequency analysis methods have gained much importance. This article discusses the basic background knowledge of the wavelet transforms and their recent applications in the processing of ECG signals for the diagnosis of various cardiovascular diseases. © 2019 Elsevier Ltd. All rights reserved.