The plastic deformation behavior of the high-entropy alloy Ag0.5CoCrCuFeNi produced in an argon-arc melt is studied for the first time at low temperatures (down to 4.2 K). Lowering the temperature from 300 to 4.2 K leads to an increase in the nominal yield strength from 450 to 750 MPa while the degree of plasticity of the alloy remains on the order of 30% over the entire range. The strain rate sensitivity is measured for deformations ε ∼ 2% by strain rate cycling. Assuming thermally activated plasma deformation, the activation volume for movement of dislocations is calculated for ε ∼ 2% and is found to vary from 122b3 at 300 K to 35b3 at 30 K, where b is the Burgers vector.