For the first time to our knowledge the mechanical properties (membrane tension and apparent viscosity) of human hepatocyte (HepG2 cell line) membranes were measured by membrane tether formation using optical trap. Membrane tension and apparent membrane viscosity were measured to be 40 ± 3 pN and 0.27±0.07 pN·s/µm respectively. The developed procedure can be used to study connections between liver cell membrane mechanics and different factors, including ethanol and drug consumption, aging, pathological processes, etc.