Internal friction measurements are made on deformed and hydrogenated Ni at frequencies of 2 Hz, 800 Hz, and 30 kHz over the temperature range between 4.2 and 373 K. Two kinds of relaxation peaksPdandPdHaccompanied by clear &Dgr;Meffects are commonly observed.Pdpeak is generated at low temperature only by plastic deformation in uncharged Ni. Electrolytic charging with hydrogen suppresses this peak but instead inducesPdHpeak at a temperature well abovePdpeak. On aging (outgassing) at temperatures between room temperature and 473 K,Pdfurther diminishes temporarily, but recovers to the original height thereafter; conversely,PdHfirst grows to a maximum height and then decays. These aging characteristics are related with nonuniform distributions of hydrogen in the samples. A good proportionality exists between the maximum height ofPdHand the height ofPdbefore H charging. In fully annealed samples wherePdis absent,PdHis not generated evidently by H charging. From these results, it is concluded thatPdpeak is ascribable to the dislocation relaxation peak of the Bordoni type, whilePdHpeak to the cold‐work peak involves the interaction between hydrogen atoms and dislocations.