This study dealt with the anti-platelet aggregation of the extracts of Curcuma longa Linn. (turmeric) rhizomes. Early research suggests that turmeric may prevent the formation of blood clots that trigger heart attack and some strokes. However, more research is needed before turmeric can be recommended for these conditions. Giemsa Microplate Assay was used to determine the anti-platelet aggregation activity. A 96-well microtitre plate was used in this study. Expression and maceration were used as methods of extraction. Pure turmeric juice and extracts that was obtained using various solvents of different polarities namely: 95% ethanol, hexane and ethyl acetate were used as test solutions at concentrations of 10 mg/mL and 100 mg/mL. Three trials in triplicate were conducted. Aspirin with a concentration of 2mg/mL was used as the positive control and normal saline solution (NSS) as the negative control. Calcium chloride (0.25M) was used to induce platelet aggregation. Platelet suspension from Type O+ blood was used. All of test solutions in NSS and in DMSO, in both 10mg/mL and 100mg/mL, showed presence of violet gels. The extracts obtained from the rhizomes of Curcuma longa Linn. (turmeric) did not show anti-platelet aggregation activity. None of the organic extracts were able to inhibit platelet aggregation. The concentrations of the test solutions were too small to exert an activity. It is recommended to increase the concentration to be able to determine if there will be an anti- platelet aggregation activity at higher concentrations. A phytochemical screening screening is recommended to determine the constituents present in the solvent-free extracts of the rhizomes of Curcuma longa Linn. (turmeric).