Khat is a flowering plant whose leaves and stems are chewed for excitement purposes in most of east African and Arabian countries. Khat can cause mood changes, increased alertness, hyperactivity, anxiety, elevated blood pressure, and heart diseases. However, the effect of khat on the heart has not been studied exclusively. The purpose of this study was to investigate the impact of khat chewing on heart activity and rehabilitation therapy from khat addiction in healthy khat chewers. ECG signals were recorded from 50 subjects (25 chewers and 25 controls) before and after chewing session to investigate the effect of khat on heart activity. In addition, ECG signals from 5 subjects were recorded on the first and eightieth day of rehabilitation therapy for investigating the effect of rehabilitation from khat addiction. All the collected signals were annotated, denoised and features were extracted and analysed. After chewing khat, the average heart rate of the chewers was increased by 5.85%, with 3 subjects out of 25 were prone to tachycardia. 1.66% QRS duration and 23.56% R-peak amplitude reduction were observed after chewing session. Moreover, heart rate variability was reduced by 19.74% indicating the effect of khat on suppressing sympathetic and parasympathetic nerve actions. After rehabilitation therapy, the average heart rate was reduced by 11.66%, while heart rate variability (HRV), QRS duration, and RR interval were increased by 25%, 3.49%, and 12.53%, respectively. Statistical analysis results also confirmed that there is a significance change (p < 0.05) in ECG feature among pre- and post-chewing session. Our findings demonstrate that, khat chewing raises heart rate, lowers heart rate variability, or puts the heart under stress by lowering R-peak amplitude and QRS duration, which in turn increases the risk of premature ventricular contraction and arrhythmia. The results also show that rehabilitation therapy from khat addiction has a major impact on restoring cardiac activity to normal levels.