The paper is concerned with a new effect of the Ultrasonic Peening treatment of the weld on the distribution of dissolved hydrogen over the binding energies. The study is carried out with the help of the hydrogen diagnostics. It is shown that a small local ultrasonic effect on the weld zone can lead to substantial hydrogen redistribution. The average binding energy of hydrogen increases, and it results in reducing its mobility and ability to form zones of local hydrogen embrittlement in both the weld and the welded material. The study of the samples after fatigue tests revealed the accumulation of hydrogen in welded joints subjected to mechanical loads. In this case, the reduction in hydrogen mobility is a good explanation for the sustainable positive effect of the periodic Ultrasonic Peening treatment of the heat affected zone during operation of structures with welded structural elements.