Lorcaserin is a new anti-obesity drug recently approved by US Food and Drug Administration. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the association of lorcaserin therapy with weight loss and adverse events in obese adults (18–65 years old). Weight loss of 3.23 kg (95% confidence interval [CI]: 2.70, 3.75) and body mass index reduction of 1.16 kg m−2 (95% CI: 0.98, 1.34) was observed compared with placebo in RCTs of 1 year duration. The use of lorcaserin for 8 and 12 weeks reduced weight of 1.60 kg (95% CI: 0.34, 2.86) and 2.9 kg (95% CI: 2.2, 3.5), respectively. In comparison to placebo, lorcaserin decreased waist circumference, blood pressure, total cholesterol, low-density lipoprotein-cholesterol and triglycerides, however did not statistically affect heart rate or high-density lipoprotein-cholesterol. Headache, nausea and dizziness were found to be significantly higher in the patients receiving lorcaserin than patients receiving placebo, whereas diarrhoea is no more likely than in patients receiving placebo. In conclusion, lorcaserin achieves modest weight loss and appears to be well tolerated. Clinical and pharmacovigilance studies with longer study duration are needed to inform of the long-term efficacy and safety of lorcaserin.