It was nearly 100 years since heparin was discovered, but the role of this widely used anticoagulant is still remarkably thought provoking now. During pathological processes such as atherosclerosis, inflammation, cancer and infection, phenomena of cell adhesion are ubiquitous and complicated. Heparin exerts anti-adhesion activity appearing as a common mechanism of its potential polypharmacology in those diseases. Furthermore, heparin can bind a variety of signalling molecules such as growth factors, cell surface proteins of pathogens and most notably, cell adhesion molecules. These signalling molecules are involved in cell communication, acting as ligands, receptors and second messengers. Considering that heparan sulphate glycosaminoglycan is increasingly recognized as a key mediator in many cellular processes, the structural similarity with heparan sulphate suggests that heparin is a multifunctional intervenor in cell communication.