Faster weaning from mechanical ventilation in ICU reduces the side effects of long-term mechanical ventilation and the cost of admission to the hospital. The objective of this study was to investigate the effect of vitamin D supplement on the facilitation of weaning in the stroke patients. In this study 99 stroke patients who were admitted to the ICU and intubated due to a fall in their level of consciousness entered the study. The level of 25 (oh) D was assessed in all of the patients and then they were divided into two different groups based on their level of vitamin D. Those included in group A (33 patients) had the vitamin D level of higher than 20 ng/ml and those in the other group (66 patients) had the vitamin D level of lower than 20 ng/ml who themselves were further divided into the two groups of B and C randomly (each consisting of 33 patients). The patients in group B received intramuscular vitamin D3 and tablet of calcium D. In the meantime, placebo was administered to the patients in group C. At the end of the intervention the mean level of vitamin D was 28.04±10.3 ng/ml in group A, 8.85±2.3 ng/ml in group B, and 10.52±4.81 ng/ml in group C. The mean durations of intubation for patients in groups A, B, and C were 13.81 days, 15.96 days, and 15 days, respectively. The patients in group A had the least duration of intubation. The three groups were significantly different as regards the duration of patients' intubation (p<0.05). However, the difference between groups B and C was not statistically significant (p>0.05). The results of this study indicate the effect of vitamin D on accelerating the weaning of patients in the intensive care unit in stroke patients.