The objective of the study was to assess the risk of serious bacterial infection (SBI) in hospitalized neonates aged ≤ 28 days with fever by history only compared to neonates with documented fever. Data regarding the presence of fever at presentation and during hospitalization, laboratory results and the diagnosis of an SBI were collected prospectively. Of the 399 neonates who met the inclusion criteria, 143 (35.8%) had fever by history only and 256 (64.2%) had documented fever at presentation. SBI was detected in 12 neonates in the history-only group (8.4%; urinary tract infection (UTI) in all cases) compared with 46 neonates with documented fever (18%; UTI in 33, UTI with bacteraemia in 4, isolated bacteraemia in 5 and pneumonia in 4). This difference was statistically significant (p = 0.008). Documented fever on admission was associated with an adjusted odds ratio of 3.23 (95% confidence interval 1.50-6.93, p = 0.003) of having an SBI. In hospitalized neonates aged ≤ 28 days, fever by history only is associated with a significantly lower rate of SBI, and particularly less invasive infections, than in neonates with documented fever. Since the risk is significantly lower, a more conservative approach to neonates without documentation of fever may be appropriate.