To investigate the electrical activity of the diaphragm during extubation readiness testing. Prospective observational trial. A 29-bed medical-surgical pediatric intensive care unit. Mechanically ventilated children between 1 month and 18 yrs of age. Twenty patients underwent a standardized extubation readiness test using a minimal pressure support ventilation strategy. A size-appropriate multiple-array esophageal electrode (electrical diaphragmatic activity catheter), which doubled as a feeding tube, was inserted. The electrical diaphragmatic activity, ventilatory parameters, and spirometry measurements were recorded with the Servo-i ventilator (Maquet, Solna, Sweden). Measurements were obtained before the extubation readiness test and 1 hr into the extubation readiness test. During extubation readiness testing, the ratio of tidal volume to delta electrical diaphragmatic activity was significantly lower in those patients who passed the extubation readiness test compared to those who failed the extubation readiness test (extubation readiness test, pass: 24.8 ± 20.9 mL/μV vs. extubation readiness test, fail: 67.2 ± 27 mL/μV, respectively; p = .02). Delta electrical diaphragmatic activity correlated significantly with neuromuscular drive assessed by airway opening pressure at 0.1 secs (before extubation readiness test: r = .591, p < .001; during extubation readiness test: r = .682, p < .001). Eight out of 20 patients had ventilator dys-synchrony identified with electrical diaphragmatic activity during extubation readiness testing. Patients who generate higher diaphragmatic activity in relation to tidal volume may have better preserved diaphragmatic function and a better chance of passing the extubation readiness test as opposed to patients who generate lower diaphragmatic activity in relation to tidal volume, indicating diaphragmatic weakness. Electrical activity of the diaphragm also may be a useful adjunct to assess neuromuscular drive in ventilated children.