Many studies show that saponins isolated from various plants have a cytotoxic effect on cancer cells inducing apoptosis and autophagy. On the other hand, saponins also exhibit a number of beneficial properties, such as antioxidant properties. Thus, saponins can be considered both in terms of their therapeutic and protective effects during anticancer treatment. In this study, we investigated the effect of the saponin fraction isolated from sea buckthorn (Elaeagnus rhamnoides (L.) A. Nelson) leaves on the viability of HL-60 cancer cells using resazurin assay and its ability to induction of apoptosis with Annexin V-FITC and propidium iodide (PI) double staining. Moreover, we studied its effect on the oxidative stress induced by H₂O₂, and anti-platelet and anticoagulant potential in whole blood using T-TAS, a microchip-based flow chamber system. We observed that the saponin fraction significantly decreased the viability of HL-60 cells at the concentration above 50 µg/mL and induced apoptosis at the concentration of 100 µg/mL. Moreover, we observed that saponin fraction used at lower concentrations, such as 0.5 and 1 µg/mL, stimulated HL-60 cells and increased their viability. The saponin fraction also decreased the level of free radicals and reduced oxidative DNA damage measured by the comet assay. However, at high concentration of oxidant H₂O₂ equal 5 mM, we noticed that the saponin fraction at 50 µg/mL increased the level of free radicals in HL-60 cells. We also demonstrated anticoagulant potential of the saponin fraction at the concentration of 50 µg/mL. Our results indicate that the saponin fraction obtained from sea buckthorn leaves can show both chemotherapeutic and chemoprotective potential.