Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children typically results in similar symptoms with other viral respiratory agents including human adenoviruses (HAdVs). Mixed HAdV and SARS-CoV-2 infection (co-infection) in children might result in enhanced or reduced disease severity compared with single infections. The present study aims to investigate the rate of SARS-CoV2 and HAdV infection and also their coinfection and compare the two infections regarding their laboratory and clinical characteristics at hospital admission. A total of 360 combined oropharyngeal and nasopharyngeal swab samples from hospitalized children were examined by real-time PCR for the existence of the SARS-CoV-2 and HAdVs. The symptoms, the clinical characteristics and laboratory findings were retrieved and compared in SARS-CoV-2 and HAdVs positive cases. Of the total 360 suspected COVID-19 hospitalized children, 45 (12.5%) and 19 (5.3%) specimens were PCR-positive for SARS-CoV-2 and HAdV respectively. SARS-CoV-2 and HAdV co-infection was detected in 4 cases (1.1%). Regarding symptoms at hospital admission, fever in SARS-CoV-2 positive group was significantly higher than that in HAdV positive group [34 (85%) vs. 7 (46.7%), p = 0.012]. However, percentages of cases with sore throat, headache, fatigue, lymphadenopathy and conjunctivitis in HAdV positive group were significantly higher than those in SARS-CoV-2 positive group. SARS-CoV-2 and HAdV co-infected children showed mild respiratory symptoms. The present study revealed that SARS-CoV-2 positive children often appear to have a milder clinical course than children with respiratory HAdV infection and children co-infected with SARSCoV-2 and HAdV had less-severe disease on presentation.