Background <p>Magnesium has an established role in respiratory physiology, but its relationship with the severity of acute exacerbations of chronic obstructive pulmonary disease (AECOPD) remains unclear. This study evaluated whether serum magnesium levels are associated with exacerbation severity in hospitalized patients with AECOPD.</p> Methods <p>In this cross-sectional study, 149 patients admitted with AECOPD in 2024 were classified into mild, moderate, or severe groups using predefined clinical and laboratory criteria at admission. Serum magnesium, oxygen saturation, arterial pH, and C-reactive protein (CRP) were measured. Group comparisons, correlation analyses, and ordinal logistic regression were performed.</p> Results <p>Hospital length of stay increased across severity categories (<i>P</i> = 0.006). Serum magnesium did not differ between mild, moderate, and severe AECOPD (<i>P</i> = 0.357), and hypomagnesemia was uncommon (7.4%) with no association with severity (<i>P</i> = 0.873). Magnesium was not correlated with oxygen saturation, arterial pH, or CRP and did not independently predict severity in ordinal logistic regression (<i>P</i> = 0.960).</p> Conclusion <p>Total serum magnesium does not appear to be a reliable marker of AECOPD severity. More physiologically relevant measures, such as ionized or intracellular magnesium, warrant further investigation.</p>