Background: Fever occurs frequently in patients with intracerebral hemorrhage (ICH) and is associated with worse functional outcomes. Rapid identification of the fever’s cause is crucial for guiding diagnostics and treatment. Data on the distribution of different fever causes in ICH are limited, and the diagnostic value of the day of fever onset remains uncertain. This study aimed to assess the distribution of fever causes in a large cohort of ICH patients and to evaluate whether temporal patterns of fever onset are associated with its underlying cause in a clinically meaningful manner. Methods: This retrospective single-center study included 547 patients with spontaneous ICH. Fever was defined as a body temperature exceeding 38.3 °C for at least two consecutive days. Fever causes were evaluated by two blinded investigators and categorized as infectious, central, or other causes. Infectious fever causes were further specified. Results: Fever occurred in 213 patients (39%) and was associated with longer hospital and ICU stays (both p < 0.01) and poor functional outcome (odds ratio 2.0, 95% CI 1.1–3.6). The three most frequent fever etiologies (>90% of cases) were pneumonia, central fever, and catheter-associated infections (i.e., urethral tract infections, ventriculitis, and central line-associated bloodstream infections). Median onset day differed across etiologies (overall p < 0.001): central fever developed earliest (2 [IQR 1–3] days), followed by pneumonia (5 [IQR 4–7] days) and catheter-associated infections (8 [IQR 5–12] days). Conclusions: In ICH, the day of fever onset may provide a useful clue to its etiology and could support clinical decision-making, but prospective validation is needed.