Introduction: Children with allergy may increase a chance to sensitize the allergic pollens with several environmental changes. Purpose of this study was to investigate the correlation with alternation of pollination associated with meteorological changes and increased sensitization rate of pollen allergens of children in Seoul metropolitan area, Korea. Methods: There were recruited 8,295 children who visited the pediatric allergic clinics at Hanyang University Seoul and Guri Hospital for allergy symptoms from January 1st, 1998 to December 31st, 2019. The pollen was collected by Burkard 7 days-sampler in 2 hospitals during the study. Meteorological data was investigated from Korea Meteorological Administration. Results: Allergic sensitization of oak, hazel, and alder pollens had the highest rate of increase among major tree pollens, an increase of 0.28% annually. The sensitization rate to pollen was increased with younger age group yearly. The duration of pollen season was 98 days in 1998, but 140 days in 2019. The duration of the pollen seasons and pollen sensitization rate to trees were positively correlated. The relationship between the sensitization rate to pollens and accumulated temperature were also correlated, positively. Conclusions: This study demonstrates the correlation between the weather changes and consequent changes of pollen seasons with increasing the sensitization rate to allergic pollens in children in Seoul metropolitan area. In addition, there was an increase in the sensitization rate in younger age group from year to year. Continuous changes in distribution of pollens raised from meteorological changes are expected from now on.