Objectives Carnosic acid (CA), which is one of bioactive compounds from rosemary, has various biological activities. However, the effect of CA on periodontal ligament cells is still uncertain. The aim of this study was to examine the effects of CA on inflammatory cytokines production in human periodontal ligament cells. Methods Cytokine and chemokine levels were measured by ELISA. Activations of signal transduction pathway were determined by Western blotting. Results Treatment of CA decreased inflammatory cytokines such as interleukin (IL)-6, CXC chemokine ligand (CXCL)10, CC chemokine ligand (CCL)2, and CCL20 productions in IL-1β or tumor necrosis factor (TNF)-α-stimulated human periodontal ligament cells in a dose-dependent manner. Moreover, we found that CA could suppress Jun-N-terminal kinase (JNK) pathway, nuclear factor (NF)-κB pathway and signal transducer and activator of transcription (STAT)3 pathway activation in IL-1β or TNF-α-stimulated human periodontal ligament cells. Conclusion The results of this study suggest that CA has anti-inflammatory effects in human periodontal ligament cells by inhibiting JNK, NF-κB and STAT3 pathways.