Ischemic stroke is one of the most common causes of severe mortality and disability worldwide. The detailed investigation of the pathophysiological mechanisms underlying this disease is among the most important tasks of modern science. The current study aims to analyze the influence of the peptide pools from the plasma of ischemic stroke patients on key hemostasis factors. 25 patients with atherothrombotic ischemic stroke and 25 patients with cardioembolic ischemic stroke were examined. The same patients also participated in a research one year after the stroke incidence. The peptide pools were isolated from the plasma by sequential precipitation with perchloric acid and ethanol. The concentration of peptide pools was measured spectrophotometrically at 210 nm. The size exclusion chromatography on Sephadex G 15 column was applied to analyze the peptide pool composition. The effects of the peptide pool on the generation and/or activity of key clotting factors like thrombin, factor Xa, and protein C were assayed using specific peptide substrates. A significant increase in the concentration of the peptides at the acute phase of the stroke was established. The changes in the composition and the content of individual molecules within the peptides pools of patients with stroke were revealed. The peptide pools of stroke patients and healthy subjects decreased ADP-induced (adenosine diphosphate) platelet aggregation and stimulated tPA (tissue plasminogen activator) secretion by endothelial cells. The effect of the peptide pools on the amidolytic activity of key hemostasis enzymes was also revealed.