To compare the effects of platelet-rich plasma (PRP) injection versus placebo (saline injection) on pain and joint function in lateral epicondylitis in randomized placebo-controlled trials. Randomized controlled trials that evaluated pain (visual analog scale [VAS] and patient-rated tennis elbow evaluation [PRTEE]) and/or functional improvement (PRTEE; disability of the arm, shoulder, and hand [DASH]; and Roles-Maudsley score [RMS]) in patients diagnosed with lateral epicondylitis and compared PRP with placebo injections were considered. The MEDLINE, EMBASE, Web of Science, and Scopus databases were searched from inception to October 2019. The assessment of bias was performed using the Cochrane Risk of Bias Tool version 1. The meta-analysis was conducted with a random effects model and generic inverse variance method. Five trials involving a total of 276 individuals were included. They used a parallel study design and saline solution as placebo. The mean age of participants was 48.0 ± 9.3 years. Follow-up varied from 2 months to 1 year. No significant changes were noted for pain (standardized mean difference [SMD], - 0.51 [95% confidence interval (CI), - 1.32 to - 0.30]) nor functional scores (SMD, - 0.07 [95% CI, - 0.46 to 0.33]) between PRP and placebo injections. The most frequent adverse reaction reported in two of the five studies was transient post-injection pain for a few days (from 16 to 20% in the PRP group and from 8 to 16% in the placebo group). PRP injection was not superior to placebo for relieving pain and joint functionality in chronic lateral epicondylitis. However, patients reported improvement after both interventions in such clinical parameters. Further randomized trials are required to determine whether PRP injection is clinically more effective than placebo (saline injection).