The inflammatory response plays a vital role in cerebral aneurysm (CA) formation and progression. Tanshinone IIA (Tan IIA) is one of the major active components of Chinese medicine Danshen (Salvia miltiorrhiza Bunge) and is widely used for the treatment of cardiovascular diseases, due to its anti‑inflammatory effects. The aim of the present study was to investigate whether Tan IIA can attenuate CA formation in rat models, and determine its underlying mechanisms. CAs were induced in rats surgically and through high‑salt diet treatments. The Tan IIA‑treated group displayed relatively mild symptoms, as compared with the control group. Tan IIA treatment reduced macrophage infiltration and nuclear factor (NF)‑κB activation in aneurysmal walls. Next, lipopolysaccharide (LPS)‑stimulated RAW 264.7 murine macrophage cells were used to examine the anti‑inflammatory effects of Tan IIA on macrophages. It was found that Tan IIA reversed LPS‑induced differentiation of RAW 264.7 cells and suppressed NF‑κB pathway activation. In conclusion, these findings demonstrated that Tan IIA can suppress CA formation by inhibiting inflammatory responses in macrophages.