Abstract Background Garlic can be considered as a useful natural herb in inhibition of inflammation. The aim of this study was to assess the effectiveness of garlic extract in lowering inflammatory markers in peritoneal dialysis (PD) patients. Methods In this parallel-designed double blind randomized clinical trial, 42 PD patients at the Shafa dialysis center, Tehran in 2017 were included. The primary outcome in this study was systemic inflammation which was evaluated by measuring the concentrations of IL-6 and CRP and ESR in serum. Results Baseline versus after-intervention median (IQR) of IL-6 (pg/ml), CRP (mg/L) and mean ± SD of ESR (mm) in garlic and placebo groups was 2.2 (0.8, 6.4) versus 0.7 (0.6, 1.2) (p