Increasing evidence shows that C‐reactive protein (CRP) is not only an inflammatory biomarker but also an important risk factor associated with ageing‐related diseases including cardiovascular disease, hypertension, diabetes mellitus, and kidney disease. Recent studies have demonstrated that CRP is pathogenic in a number of diseases including hypertensive cardiovascular and kidney complications, diabetic nephropathy, and acute and chronic kidney diseases. It is well known that CRP binds its receptor, CD32/CD64, to induce the process of inflammation by activating the NF‐κB signalling pathway. In addition, CRP mediates tissue fibrosis in a number of cardiovascular and kidney diseases by activating TGF‐β/Smad signalling via TGF‐β1‐dependent and independent mechanisms. Furthermore, CRP is able to activate mTOR signalling in the diabetic conditions. Our recent studies also revealed that CRP impairs cell regeneration by causing the G1 cell cycle arrest and promotes ageing via a Smad3‐dependent p21/p27 mechanism. In this review, we discuss the roles of CRP in ageing, with a focus on its function and mechanisms in physiological or “healthy” ageing, in ageing‐related diseases, and in cell signalling.