Introduction: The calcium ion (Ca2+) is a ubiquitous intracellular messenger during and immediately after an ischemic period. Clinical studies suggest that severity of clinical symptoms, prognosis and infarct volume are also associated with levels of serum calcium. Aim: The aim of this study is to determine Serum calcium as a marker of severity in acute ischaemic stroke patients. Methodology: This prospective observational study was conducted on 80 patients of acute ischemic stroke admitted in the department of medicine at Jhalawar medical college, Jhalawar during the period of 1 year. Adjusted serum calcium level was obtained within 72 hours from onset. Results: Out of 80 patients of acute ischemic stroke, 49 (61.25%) had low serum calcium while 31 (38.75 %) participants had normal level of serum calcium. Most common age group was 61 to 70 years (36.7%). NIHSS score was higher with low serum calcium level. Out of the 49 patients who had low levels of calcium, 49% (24) had severe stroke with NIHSS score 21-42. Among 49 patients with low serum calcium, 91.5% (45) had poor outcome. MRS score was higher with low serum calcium level. Chi square analysis revealed lower adjusted serum calcium levels accompanied by poor outcome statistically significant (p= <0.0103). Conclusion: Based on these results, we can conclude that low adjusted calcium levels in patients with acute ischemic stroke is an independent risk factor and have poor outcome than patients with normal serum adjusted calcium level.