A systematic investigation is made on the solid solution hardening of binary nickel alloys with additions of B-subgroup and transition metal elements. The 0.2% flow stress at 77 K and the Young’s modulus are measured for a variety of binary alloys to evaluate the rate of solution hardening per one atomic percent of solute (dσ⁄dc) and that of change in elastic constant (dE⁄dc). Together with the available data on the rate of change in lattice constant (da⁄dc), interpretation of the solution hardening is attempted in terms of the elastic interaction theory. It is found that dσ⁄dc for the additions of B-subgroup elements is linearly related with a combined parameter appropriate for the elastic interaction between solutes and edge dislocations, where the contribution of modulus misfit is minimal and atomic size misfit governs the hardening. It is also found that for the additions of transition metal elements there is an extra hardening over what is expected from the same treatment on B-subgroup elements. These findings are the same in nature as what has been observed in the solution hardening of an L1₂ intermetallic compound Ni₃Al. The reason for the extra hardening by transition metal elements is discussed, and a possible contribution of electronic interaction involving d-electrons is suggested for the solution hardening by a transition metal solute in the transition metal solvent, nickel.