Coumarins are of many different structures. They constitute an important class of pharmacological agents possessing a range of different physiological activities including anti-cancer, anti-oxidant, anti-inflammation, anti-HIV, anticoagulant, anti-bacterial, analgesic and comparative immune-modulation. Recently, coumarins have attracted intense research interest. Of great interest is the possibility that this class of molecules could be a source of drugs for the therapy of several diseases. These include recent insights into inhibiting cell proliferation by interfering with mitotic spindle microtubule function, decrease Matrix Metalloproteinase (MMP) activity, block the cell cycle in the S or G2/M phases to interfere with processes of cell division, suppress O2 - generation in leukocytes, inhibit different protein kinases, modulate the signalings, induce carcinogen-detoxifying enzymes glutathione Stransferases (GSTs) and/or NAD(P)H quinine oxidoreductase (NQO1), suppress the phosphorylation of Akt/PKB as a mechanism inhibiting inflammation, progress in structure modification to increase in anti-fungal action, to broaden against bacteria spectrum, to enhance inhibiting activities of nitric oxide synthase (NOS) and cyclooxygenase (COX), to strengthen anti-oxidant activity and to exhibit a much higher cytotoxicity against human umbilical vein endothelial cell (HUVEC). With fewer non-hemorrhagic side effects than the indanedione derivatives, they can be applied as an oral anticoagulant commonly for preventing venous thromboembolism following orthopedic surgery, recurrent myocardial infarction and the treatment of systemic embolism in atrial fibrillation, together with the significant advances in the basis of drug action. It is therefore useful to build up some correlations with the data available in order to better explore the molecular and cellular mechanism of coumarin action in the treatment of diseases. This review will focus on recent advances in molecular and cellular mechanisms of coumarin action involved with the relationship between structure and activity.