OBJECTIVES: Mepolizumab is a monoclonal antibody that inhibits interleukin-5, which is a principle cytokine in eosinophil differentiation, maturation, recruitment and activation at sites of allergic inflammation. We sought to evaluate the efficacy and safety of mepolizumab as compared to placebo in patients with chronic asthma.  METHODS: We searched Pubmed, EMBASE, ClinicalTrials.gov and references of the included trials from inception till January 2016 for efficacy and safety data pertaining to mepolizumab for the treatment of chronic asthma. Two reviewers independently searched, extracted data and assessed risk of bias using the Jadad scale and differences were adjudicated via consensus discussion. The primary outcomes included were eosinophil counts in blood and sputum, exacerbations, and forced expiratory volumes. Secondary outcome was adverse events due to mepolizumab.  RESULTS: A total of seven randomized placebo controlled trials (RCTs) involving 1910 participants were included. Mepolizumab significantly reduced eosinophils in blood samples (Mean Difference [MD] -0.33X10/L, 95% Confidence Interval [CI] -0.50 to -0.16; 3 studies, 311 participants) and sputum eosinophils (MD -6.22X10/L, 95% CI -9.63 to -2.82; 2 studies, 80 participants) and also reduced the risk of exacerbation (odds ratio [OR], 0.49, 95% CI 0.25 to 0.93; 3 studies, 323 participants) as compared to placebo. However, no significant differences were found for forced expiratory volume in 1 second (FEV1) (MD, 0.01, 95% CI -0.16 to 0.17; 2 studies, 250 participants) and FEV1% of predicted value (MD 0.91, 95% CI -5.85 to 7.67; 2 studies, 314 participants). The common adverse events reported with mepolizumab were headache, chest pain, nasopharyngitis, erectile dysfunction, fatigue, rash, upper respiratory tract infection and sinusitis.  CONCLUSIONS: Mepolizumab significantly lowers blood and sputum eosinophil counts, and also effectively reduces asthma exacerbation frequency, though it shows no significant improvement on functional airway outcome. Further larger RCTs are needed to confirm these findings.