The dissolution behavior of a single H₂ bubble electrochemically generated at a Pt microelectrode in 1 M H₂SO₄ was studied. The open circuit potential (OCP) relaxation after the polarization end was recorded and correlated with the dissolved H₂ concentration at the interface electrode/electrolyte/gas. Simultaneously, the shrinking of the bubble was followed optically by means of a high speed camera. In addition, analytical modeling and numerical simulations for the bubble dissolution were performed. Three characteristic regions are identified in the OCP and the bubble radius transients: (i) slow relaxation and shrinking, (ii) transition region, and (iii) a long-term slowed down dissolution process. The high supersaturation after polarization remains longer than theoretically predicted and feeds the bubble in region (i). This reduces the dissolution rate of the bubble which differs significantly from that of nonelectrochemically produced bubbles. Numerical multispecies simulations prove that oxygen and nitrogen dissolved in the electrolyte additionally influence the bubble dissolution and slow down its shrinkage compared to pure hydrogen diffusion. In region (iii), a complete exchange of hydrogen gas with nitrogen and oxygen has occurred in the gas bubble.