We sought to determine whether awareness of the pediatric appropriate use criteria (AUC) affected transthoracic echocardiogram (TTE) ordering by cardiologists; evaluate for differences in classification of an encounter’s AUC clinical scenario by investigator chart review compared with clinicians at the time of the encounter; and assess TTE yield by appropriateness rating. AUC clinical scenario(s) were assigned to patients without prior TTE by investigator chart review of visits in 2014 (n = 209) and 2016 (n = 199), and by clinician classification in 2016 (n = 671). Investigators documented TTE utilization and findings. Between 2014 and 2016, TTE utilization decreased from 54 to 33% (p < 0.001) of “rarely appropriate” (R) encounters, resulting in a decrease in overall TTE utilization from 73 to 55% of encounters (p < 0.001). There was only moderate agreement of AUC appropriateness by investigator chart review and clinician classification (κ = 0.533, p < 0.001). Abnormal TTE findings were detected in 18.7% of R encounters, with 21 of 24 abnormalities in infants younger than 4 months presenting with murmur. A decrease in TTE utilization for R encounters may represent a change in practice from increased awareness of the AUC. AUC scenario classification by clinicians at the time of the encounter could be superior to chart review. TTE abnormalities may be missed in infants younger than 4 months of age when evaluated for murmurs with the AUC.