The present work investigates the effect of confinement on the hydrogen bonding interactions in H₂S dimers. The interiors of different sized fullerenes (C₆₀, C₇₀, C₈₄, and C₁₂₀) have been used to model the effect of confinement. It was found that as the degree of confinement increases, the hydrogen bonding between H₂S molecules disappears and sulphur–sulphur interactions appear. We obtained clear computational evidence that, inside C₆₀, the H₂S dimer is bound by a covalent bond between two sulphur atoms. It was also found that the strength of the S–S bond inside fullerenes is linked to the amount of charge transfer from the H₂S dimer to the fullerene.