Background The frequency of influenza virus infections and group A beta-hemolytic streptococcus (GAS) pharyngitis varies according to populations. We aimed to investigate the frequency of influenza virus and streptococcal pharyngitis infections in a pediatric outpatient cohort with many pediatric admissions in Istanbul. Materials and methods Children with upper respiratory tract infection (URTI) symptoms between 2011 and 2018 who underwent rapid diagnostic tests for influenza virus or streptococcal infection were evaluated retrospectively. Results The total number of pediatric cases admitted between 2011 and 2018 was 185,228, of which 119,928 were under five years old and 66,300 were children over five years old. The mean frequency of the influenza virus was 1,283 per 100,000 children, and the mean frequency of streptococcal pharyngitis was 1,764 per 100,000 children. The frequency of influenza has increased over the years. The frequency of streptococcal infection is higher in children over five years of age, and its frequency has decreased in this group. Conclusions The frequency of influenza virus infection and GAS pharyngitis varies according to years and seasons. Winter and spring were the seasons with the most frequent positive influenza virus and GAS pharyngitis. Although influenza frequency increased annually, this phenomenon was not observed in the frequency of GAS pharyngitis.