Intermetallic Sm(Fe1−xCox)2compounds having the cubic MgCu2‐type structure absorb a small quantity of hydrogen from the atmosphere under normal conditions. A magnetic annealing of such samples leads to the induction of a gigantic magnetic uniaxial anisotropy, which is linked to the ordered distribution of hydrogen into interstitial sites of the lattice. In this paper the induced magnetic anisotropy and spontaneous lattice distortions are studied as a function of both composition and hydrogen content. It is shown that the induced uniaxial anisotropy which adds to the initial cubic anisotropy gives rise to the occurrence of first‐order magnetization processes (FOMP). In the temperature range where spin reorientation transitions take place a peculiar behavior of the FOMP is observed.