In this case report, we describe two repeated transcutaneous electromyography of the diaphragm (dEMG) measurements in an infant with suspected paresis of the right hemidiaphragm after cardiac surgery. The first measurement, performed at the time of diagnosis, showed a lower electrical activity of the right side of the diaphragm in comparison with the left side. The second measurement, performed after a period of expectative management, showed that electrical activity of the affected side had increased and was similar to the activity of the left diaphragm. This finding was accompanied by an improvement in the clinical condition. In conclusion, repeated measurement of diaphragmatic activity using transcutaneous dEMG enables the observation and quantification of spontaneous recovery over time. This information may assist the clinician in identifying patients not responding to expectative management and in determining the optimal timing of diaphragmatic surgery.