Garcinia combogia is a flowering plant with a wide range of medicinal uses which include antiparasitic, antimicrobial, antithrombotic, antidiabetic, antihepatotoxic and as purgative. However its antithrombotic properties have not been fully elucidated hence this present study. In this study, we investigated the antithrombotic activities of the methanolic seed extracts of Garcinia combogia in comparison with a known standard drug (aspirin) as the positive control and Normal saline as the negative control. The work is purely an experimental research on rats. The result showed that both the bleeding time and clotting time were prolonged and dose dependant but not superior to the standard drug (aspirin), while the platelet count was reduced showing that the methanolic seed extract of Garcinia combogia has antithrombotic properties. Also the extract tested positive to the following phytochemical compounds – alkaloids, glycosides, flavinoids, resins, proteins and tannins after phytochemical analysis following a standard procedure which confer on the plant other medicinal properties. Finally, we recommended that further work be done to establish the mechanism of action of its antithrombotic activities and to use this plant to develop better alternatives than the present drugs currently used in clinical medicine.