In Brugada syndrome (BrS), spontaneous type 1 electrocardiogram (ECG) is an established risk marker for fatal arrhythmias whereas drug-induced type 1 ECG shows a relatively benign prognosis. No study has analyzed the prognosis of fever-induced type 1 ECG (F-type1) in a large BrS cohort. The objectives of this study were to assess the prognosis of F-type1 in asymptomatic BrS and to compare the effects of fever and drugs on ECG parameters. One hundred twelve patients with BrS who developed F-type1 were retrospectively enrolled. Prognosis was evaluated in 88 asymptomatic patients. In a subgroup (n = 52), ECG parameters of multiple ECGs (at baseline, during fever, and after drug challenge) were analyzed. Eighty-eight asymptomatic patients had a mean age of 45.8 ± 18.7 years, and 71.6% (67 of 88) were men. Twenty-one percent (18 of 88) had a family history of sudden cardiac death, and 26.4% (14 of 53) carried a pathogenic SCN5A mutation. Drug challenge was positive in 29 of 36 patients tested (80.6%). The risk of ventricular fibrillation in asymptomatic patients was 0.9%/y (3 of 88; 43.6 ± 37.4 months). ST-segment elevation in lead V2 during fever and after drug challenge was not significantly different (0.41 ± 0.21 ms during fever and 0.40 ± 0.30 ms after drug challenge; P > .05). Fever shortened the PR interval compared to baseline, whereas drug challenge resulted in prolonged PR interval and QRS duration (PR interval: 169 ± 29 ms at baseline, 148 ± 45 ms during fever, and 202 ± 35 ms after drug challenge; QRS duration: 97 ± 18 ms at baseline, 92 ± 28 ms during fever, and 117 ± 21 ms after drug challenge). Patients with BrS who develop F-type1 are at risk of arrhythmic events. F-type1 appears to develop through a more complex mechanism as compared with drug-induced type 1 ECG.