To assess diagnostic imaging utilization and the proportion of negative appendectomies for pediatric appendicitis at US children's hospitals between 2004 and2018. This was a retrospective study using data from the Pediatric Health Information System (PHIS) database. Pediatric patients (age: 0-17 years) who underwent an appendectomy at one of 32 children's hospitals from January 1, 2004, through September 30, 2018, were included. Patients were identified based on International Classification of Diseases, 9th revision and International Classification of Diseases, 10th revision procedure codes. Patient demographics, imaging performed, and the frequency of negative appendectomy were analyzed. The final study population consisted of 104,033 children. From 2004 to 2018, CT utilization decreased from 56.8% (2,951 of 5,198) to 18.6% (1,201 of 6,455; P < .001). Ultrasound utilization increased from 26.4% (1,371 of 5,198) to 63.4% (4,093 of 6,455; P < .001). Radiography utilization remained stable at 16.7% (870 of 5,198) and 15.8% (1,018 of 6,455; P= .160). MRI use increased from 0.1% (6 of 5,198) to 2.2% (143 of 6,455; P < .001). During the study period, the negative appendectomy rate slightly decreased, from 3.74% (4,742 of 126,778 in 2004-2011) to 3.14% (4,258 of 135,561 in 2012-2018; P < .001). There has been a shift in imaging of children with appendicitis over 15 years in the United States, because the use of CT has decreased and ultrasound use has increased. This shift has likely added value to the health care system without adversely affecting outcomes (negative appendectomy rate).