In 2014, an outbreak of adenoviral pneumonia occurred in the Korean military training center. However, there are limited data on the characteristics of the fever and its response to antipyretic therapy in immunocompetent adults with adenovirus-positive community-acquired pneumonia (CAP). The medical records of the patients who were admitted to the Armed Forces Chuncheon Hospital for the treatment of CAP between January 2014 and December 2016 were retrospectively analyzed. The patients were divided into three groups, namely, the adenovirus-positive (Adv) group, the adenovirus-negative (Non-Adv) group and the unknown pathogen group, according to the results of a polymerase chain reaction (PCR) test and sputum culture used to measure adenovirus and other bacteria or viruses in respiratory specimens. We evaluated and compared the demographics, clinicolaboratory findings and radiological findings upon admission between the two groups. Out of the 251 military personnel with CAP during the study periods, 67 were classified into the Adv group, while 134 were classified into the Non-Adv group and 50 were classified into the unknown pathogen group. The patients in the Adv group had a longer duration of fever after admission (3.2 ± 1.6 vs. 1.9 ± 1.2 vs. 2.2 ± 1.5 days, P = 0.018) and symptom onset (5.8 ± 2.2 vs. 3.9 ± 2.5 vs. 3.7 ± 2.0 days, P = 0.006) than patients in the Non-Adv and unknown pathogen groups, respectively. The patients in the Adv group had a higher mean temperature at admission (37.8 ± 0.3 vs. 37.3 ± 0.3 vs. 37.3 ± 0.3, P = 0.005), and more patients were observed over 40 and 39 to 40(14.9% vs. 2.2% vs. 4.0%, 35.8% vs. 3.7% vs. 6.0%, P <  0.001) than those in the Non-Adv and unknown pathogen groups, respectively. The Adv group more commonly had no response or exhibited adverse events after antipyretic treatment compared to the Non-Adv group (17.9% vs. 1.5%, 35.0% vs. 4.3%, P <  0.001, P = 0.05, respectively). In addition, the time from admission to overall clinical stabilization was significantly longer in the patients in the Adv group than in those in the Non-Adv group (4.3 ± 2.8 vs. 2.9 ± 1.8 days, P = 0.034, respectively). Furthermore, no significant difference in the length of hospital stay was observed between the two groups, and no patient died in either group. In this study, Adv-positive CAP in immunocompetent military personnel patients had distinct fever characteristics and responses to antipyretic treatment.