Urticaria is a common pediatric skin disorder. Histamine H1-receptor antagonists are effective in chronic as well as acute urticaria. When H1-anti-histamines are ineffective, add-on use of H2-receptor antagonists is thought to give better symptom relief. However, there are few reports on the therapeutic efficacy in pediatric patients. We retrospectively reviewed the medical records of pediatric patients with chronic spontaneous urticaria (csU) who met the following criteria. They were consulted our outpatient clinic between April 2010 and March 2012; were unsuccessfully treated with H1 antihistamines; and were treated with add-on H2-receptor antagonist (famotidine). In six patients who met the inclusion criteria (mean age 6.1 ± 5.1 years), urticaria activity score was significantly decreased from 4.3 ± 0.8 just before administration of famotidine to 1.3 ± 1.0 on the first outpatient visit within 4 weeks after the first administration of famotidine (p < 0.0001). No adverse effects of famotidine were observed. Although this study has a limitation of small subjects, our results suggest the potential efficacy of add-on use of H2-receptor antagonists and might justify extending the range of application of H2-receptor antagonists to pediatric patients with csU.