Annealed and tensile prestrained 316L-type stainless steel is studied by internal friction (IF) method. Low-frequency forced-vibration measurements of IF are carried out in the temperature range of 130—500 K before and after gaseous-hydrogen charging at 543 K and under three different pressures: 0.5, 10, and 100 MPa. Two complex multicomponent IF peaks at about 250 and 365 K are detected after preliminary tensile deformation in hydrogen-free material. As revealed, the low-temperature peak is of relaxation type, and the high-temperature one is a resonant peak. The effect of hydrogen content and hydrogen distribution on IF peaks’ features, e.g., background, amplitude and thermal stability, is examined. An increase in stability of vacancies caused by hydrogen is suggested that follows from IF measurements after ageing at 473 K. As experimentally shown, the temperature drop of hydrogenation to 358 K leads to a marked shift of the high-temperature peak toward higher temperatures. A hypothesis about the cause underlying this phenomenon is proposed.