Ischemia and stroke are the top ten deadliest diseases in the world, where both of these diseases are related to blockage of blood vessels. Clopidogrel as an antiplatelet agent for the therapy for those diseases still has many side effects. The treatment with Carica papaya L. extract containing alkaloid compounds, traditionally has an anti-platelet effect. This research aimed to observe antiplatelet activity of chloroform extract of Carica papaya L. leaves by in-silico study into ADP (Adenosin Diphosphate) receptor and in-vitro study of platelet rich plasma induced by ADP which was observed with spectrophotometer UV/Vis method. Based on the results of in-silico study, alkaloid compounds such as dehydrocarpain I, dehydrocarpain II and emetin have docking score (-121.77 until -142.75 Kcal / mol) had lower binding energy than Clopidogrel (-111.09 Kcal / mol) toward ADP receptor. The result of in-vitro study, found that the addition of 100 ppm of chloroform fraction extract oí Carica papaya L. leaves inhibited platelet aggregation about 2.55% ± 0.36, which was better than the standard drug, Clopidogrel (2.13% ± 0.34). Based on the results of in-silico and in-vitro study, the chloroform fraction extract of Carica papaya L. which contained alkaloid compounds, had activity to inhibit platelet aggregation, therefore they are potential to be developed as new drugs. © 2022 American Institute of Physics Inc.. All rights reserved.