Atherosclerosis, leading to formation of plaque on the artery vessel wall, underpins many cerebral and cardiovascular diseases with high mortality rates globally. Nanoparticles promise to advance strategies to treat atherosclerotic disease. Through the rational design of nanoparticles, nano-based delivery systems enable more efficient delivery of a drug to its therapeutic target or even directly to the diseased site, overcoming biological barriers and enhancing a drug’s therapeutic index. In addition, advances in imaging techniques have led to the development of theranostic nanoparticles that may simultaneously act as carriers of both imaging and therapeutic payloads. The following is a summary of nanoparticle diagnosis for atherosclerosis and an overview of recent major advances in the targeted treatment of atherosclerotic disease.