Green tea is known to contain antiviral components that prevent influenza infection. A limited number of adult clinical studies have been undertaken, but there is a paucity of clinical evidence concerning children. We conducted an observational study to determine the association between green tea consumption and the incidence of influenza infection among schoolchildren. Anonymous questionnaire surveys were undertaken twice during the influenza season from November 2008 to February 2009 (endemic seasonal type A influenza infection); each survey was conducted for 2663 pupils across all elementary schools in Kikugawa City (a tea plantation area), Japan. Each questionnaire was completed and submitted by 2050 pupils (response rate, 77.0%; age range, 6-13 y). The adjusted OR associated with the consumption of green tea for ≥6 d/wk compared with <3 d/wk was 0.60 [(95% CI = 0.39-0.92); P = 0.02] in cases of influenza confirmed by the antigen test. Meanwhile, the adjusted OR inversely associated with the consumption of 1 cup/d to <3 cups/d (1 cup = 200 mL) and 3-5 cups/d compared with <1 cup/d were 0.62 [(95% CI = 0.41-0.95); P = 0.03] and 0.54 [(95% CI = 0.30-0.94); P = 0.03], respectively. However, there was no significant association with the consumption of >5 cups/d. Our findings thus suggest that the consumption of 1-5 cups/d of green tea may prevent influenza infection in children.