Background Platelet-to-lymphocyte ratio (PLR) and neutrophil-to-lymphocyte ratio (NLR) have been reported to reflect the inflammatory response and disease activity in a variety of autoimmune diseases. Objectives This study aimed to evaluate the value of PLR and NLR as markers to monitor disease activity in Takayasu's arteritis (TAK). Methods A retrospective case-control study involving 88 patients with TAK and 78 healthy controls was performed. We compared the PLR and NLR between patients and healthy controls, and also analysed the correlations between PLR or NLR and indices of TAK disease activity. Results Increased PLR and NLR were observed in patients with TAK. PLR was positively correlated with hs-C-reactive protein (hs-CRP) (r=0.239, p=0.010) and erythrocyte sedimentation rate (ESR) (r=0.270, p=0.010). NLR also exhibited a positive relationship with Kerr's score (r=0.284, p=0.002), hs-CRP (r=0.313, p=0.006) and ESR (r=0.249, p=0.019). A PLR level of 183.39 was shown to be the predictive cut-off value for TAK (sensitivity 37.8%, specificity 93.0%, area under the curve (AUC)=0.691). A NLR level of 2.417 was found to be the predictive cutoff value for TAK (sensitivity 75.6%, specificity 55.8%, AUC=0.697). Conclusions PLR and NLR could be useful markers to reflect inflammation and disease activity in patients with TAK.