The structure of Sally modules of \(\fkm\)-primary ideals \(I\) in a Cohen-Macaulay local ring \((A, \m)\) satisfying the equality \(\e_1(I)=\e_0(I)-\ell_A(A/I)+1\) is explored, where \(\e_0(I)\) and \(\e_1(I)\) denote the first two Hilbert coefficients of \(I\).