Background and Purpose- Acute stroke treatment is challenging, and stroke remains a major cause of death and disability. The purpose of this meta-analysis is to investigate the effects of postacute stroke intravenous administration of the neuroprotectant magnesium sulfate (MgSO) on global outcome, functional outcome, and mortality 90 days poststroke (ischemic and nonischemic). Methods- We searched in Pubmed, Science Direct, CENTRAL, and ClinicalTrials.gov, up to November 11, 2017, and we conducted a systematic review and meta-analysis of randomized controlled trials. We synthesized results by using random-effects model, weighted mean differences, standardized mean differences, and odds ratios. Results- Seven randomized controlled trials (4347 patients) met our criteria. Compared with placebo, treatment did not improve functional outcome defined as Barthel Index >60 (odds ratio =1.05; 95% CI, 0.92-1.19) and >95 (odds ratio =0.95; 95% CI, 0.76-1.20), 90 days poststroke. It also did not improve global outcome measured with modified Rankin Scale (standardized mean difference =-0.01; 95% CI, -0.12 to 0.10), 90 days poststroke. In an additional subgroup meta-analysis that exclusively included ischemic stroke patients, intravenous MgSO resulted in lower modified Rankin Scale score (improved global outcome; weighted mean difference =-0.96; 95% CI, -1.34 to -0.58; I=0%], 90 days poststroke. Finally, mortality stayed unaltered (odds ratio =1.10; 95% CI, 0.94-1.29). Conclusions- The findings of our meta-analysis showed that intravenous MgSO generally did not improve global/functional outcomes and mortality at 90 days after stroke (combined ischemic stroke and nonischemic stroke). The finding of favorable neurological outcome, selectively in ischemic stroke patients, should be viewed with extreme caution given the limited number of patients included in this subgroup meta-analysis.