Despite the technical importance of mechano-sorptive creep in paper, the exact mechanism behind this phenomenon is still not fully understood. In this study it was shown that the mechanosorptive creep of paper sheets can be signiﬁcantly reduced by chemical cross-linking through periodate oxidation. The mechanism behind this reduction has been examined through creep measurements of both sheets and individual ﬁbres. For sheets the creep acceleration due to varying humidity was signiﬁcantly reduced by the chemical cross-linking. For single ﬁbres, however, the creep acceleration was not affected by the chemical crosslinking. In fact the absolute creep rate for the periodate oxidised ﬁbres were higher than that of the reference ﬁbres. This clearly showed that the improvement in mechano-sorptive creep found on a sheet level does not originate from an improved creep resistance for individual ﬁbres but rather from mechanisms operating at the ﬁbre network level. Hygroexpansion and moisture sorption of the sheets during the humidity cycling used for creep testing have also been measured, and the results showed that both was reduced by the periodate oxidation. Reduced moisture sorptivity and hygroexpansion probably minimises stress concentrations at the ﬁbre network level and thereby also the creep acceleration.