Extended-spectrum β-lactamase (ESBL)-producing-Enterobacteriaceae strains were detected in 12% (6 out of 50) of fecal samples collected from the inpatients of a Japanese pediatric hospital. All the ESBLs belonged to the CTX-M-1 group. The proportion of carriage of ESBL producers was higher among patients who had received antibiotics within the past 3 months and among those who had cardiologic diseases.