In this paper we examine the elastic (c′ and c₄₄) and magnetostrictive (λ₁₀₀ and λ₁₁₁) behaviors of Fe_100−xGe_x for 4<x<18, quantities used further to find the fundamental magnetoelastic coupling constants b₁ and b₂ at room temperature. The x dependence ofb₁ and b₂ for Fe_100−xGe_x is contrasted to those of Fe_100−xGa_x and Fe_100−xAl_x. While the rhombohedral shear elastic constant c₄₄ is almost insensitive to the type and amount of solute, the tetragonal shear constant c′ shows a pronounced and rapid softening with increasing x for all three alloys but with different decreasing slopes. Similarly, while the rhombohedral magnetostriction λ₁₁₁ behavior is analogous for all three alloy systems, showing a sign change from negative to positive at the onset of chemical order, the tetragonal magnetostriction λ₁₀₀ behavior differs. For the Ga and Al alloys, λ₁₀₀ maintains positive values over the entire x range, both curves showing large peak values, whereasλ₁₀₀ of Fe_100−xGe_x exhibits a moderate positive peak followed by a negative dip, both of comparable magnitude. Finally the tetragonal coupling constant −b₁ of Fe–Ge shows a marked, sharp decrease as chemical order occurs at x ∼ 12 at. % Ge. The decline continues until the ordered D0₃ phase is fully established at x ∼ 18 at. % Ge. The peak value of |b₁| for Fe–Ge is approximately half of those for Fe–Ga and Fe–Al. This smaller value of |b₁|, obtained for the higher electron concentration Ge alloy, is consistent with predictions based on band structure calculations. The rhombohedral coupling constant−b₂ shows a consistent sign change at the occurrence of chemical ordering in both Fe–Ga and Fe–Ge.