Background: Acute Exacerbations of Chronic Obstructive Pulmonary Disease (AECOPD) is a common reason for hospitalization and a major cause of death and disability worldwide. Intravenous MgSO4 has shown benefits in acute severe asthma by producing bronchodilation. However, the use of intravenous MgSO4 in acute exacerbations of COPD alone or as an adjuvant to bronchodilators is lacking and more studies are needed to establish its usefulness. Aim/Objectives: To study the role of serum magnesium in acute exacerbation of COPD. To study the role of intravenous magnesium sulfate in acute exacerbation of COPD. Methods: A non-randomized, open-label, parallel-group, placebo-controlled, comparative prospective interventional study, where 100 subjects were allotted into 2 groups (group M and group P) of 50 each to receive either 2g of intravenous MgSO4 or a similar amount of normal saline as placebo along with nebulized salbutamol. The efficacy of MgSO4 was evaluated by measuring PEFR a primary outcome parameter at 0,15,30 and 45 mins. Irrespective of the group serum magnesium of all 100 patients are monitored at the time of admission Statistical Analysis: The statistical software SPSS V.16.0 was used for all analysis of the data &MS Word & Excel have been used to generate graphs, tables, etc. All the results are presented as mean ± SD & the range values for the continuous data. The categorical data are presented as numbers & percentages. A p-value of ≤0.05 was considered statistically significant. Result: The mean difference in the MgSO4 group at every observation was higher than the placebo. The mean change in PEFR (193.04± 43.47) in the MgSO4 group at 45mins observation was Significantly (p=0.0170) higher than in placebo (172.4± 41.47). The serum magnesium level was also monitored but our study was not able to prove a significant correlation between hypomagnesemia and acute exacerbation of COPD. Conclusions: The benefits of intravenous MgSO4 as an adjuvant to bronchodilators in AECOPD resulted in improvement of clinical condition and PEFR. The improvement in PEFR was significantly higher with MgSO4 than with placebo MgSO4 enhances the early bronchodilator response of other drugs and has significant efficacy.