Recently, nonthermal atmospheric pressure plasma has been used in medical devices for sterilization, blood coagulation, induction of apoptosis in cancer cells, etc. The purpose of this study is to evaluate the impact of cold atmospheric plasma on coagulation time in patients under treatment with warfarin as an anticoagulant agent (group A) and to compare this impact in healthy persons (group B). To measure the coagulation time, Clotting Time (CT) is used. After obtaining informed consent from each subject, two venous blood samples are taken to check CT. One sample is processed with plasma (case sample) and the other sample is not processed with plasma. CT in both samples is measured by a physician and recorded in a form in addition to demographic characteristics and drug history. The data are analysed using Statistical Package for the Social Sciences (SPSS) software. The Mann-Whitney test is used for comparison between groups and the Wilcoxon signed-ranks test is used to compare the difference between CT before and after plasma processing. The results show the significant effect of plasma on the reduction of plasma coagulation time, and this reduction is higher in the warfarin-treated group.