The aim of this study was to compare the evolution of systemic cytokine levels over time in patients with pneumococal pneumonia treated either with β-lactam monotherapy or with combination therapy (β-lactam plus fluoroquinolone). Prospective observational study of hospitalized non-immunocompromised adults with PP. Concentrations of IL-6, IL-8, IL-10, and TNF-α were determined on days 0, 1, 2, 3, 5, and 7. Patients on β-lactam monotherapy were compared with those receiving combination therapy. Fifty-two patients were enrolled in the study. Concentrations of IL-6, IL-8, and IL-10 decreased rapidly in the first days after admission, in accordance with the mean time to defervescence. High levels of IL-6 were found in patients with the worst outcomes, measured by the need for intensive care unit admission and mortality. No major differences in demographic or clinical characteristics or severity of disease were found between patients treated with β-lactam monotherapy and those treated with combination therapy. IL-6 levels fell more rapidly in patients with combination therapy in the first 48 h (p = 0.016). Our data suggest that systemic expression of IL-6 production in patients with PP correlates with prognosis. Initial combination antibiotic therapy produces a faster decrease in this cytokine in the first 48 h.