Previous reports have associated hyperglycemia to poor outcome among aged and comorbid Staphylococcus aureus bacteraemia (SAB) patients. However, the prognostic impact of hyperglycemia in SAB irrespective of age and underlying conditions including a diagnosis of diabetes has received little attention. The objective here was to evaluate the prognostic relevance of hyperglycemia at onset of methicillin-sensitive SAB (MS-SAB). It was a retrospective study of MS-SAB patients. Blood glucose was measured within 24 h of positive blood cultures. The patient cohort was analyzed en bloc and by categorization according to age, underlying conditions and a diagnosis of diabetes. Altogether 161 patients were identified. High initial blood glucose levels were observed among diabetics (p < 0.001), patients with deep infections (p < 0.05) and poor outcome at 28- or 90-days (p < 0.05). Receiver operating characteristics presented the glucose cut-off level of 7.2 mmol/L as a significant predictor of mortality with an area under the curve of 0.63 (95% CI 0.52-0.75, p < 0.05). Blood glucose ≥7.2 mmol/L connected to higher 28- (9 vs. 20%, p < 0.05) and 90-day (14 vs. 29%, p < 0.01) mortality. In Cox proportional hazard regression the blood glucose cut-off value of 7.2 mmol/L significantly predicted 90-day mortality (HR, 2.12; 95% CI, 1.01-4.46; p < 0.05). Among young and healthy non-diabetics the negative prognostic impact of high glucose was further accentuated (HR 7.46, p < 0.05). High glucose levels had no prognostic impact among diabetics. Hyperglycemia at SAB onset may associate to poor outcome. The negative prognostic impact is accentuated among young and healthy non-diabetics.