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An efficient ${\text{Nd}}^{3+}\to {\text{Yb}}^{3+}$ energy transfer in a new series of alkali-free barium-alumino-metaphosphate glasses with a transfer efficiency reaching up to 95% has been reported here. It is due to the effective phonon assistance arising with the excellent matching of the present host phonon energy with the energy mismatch between ${\text{Nd}}^{3+}$ $\left({{}^{4}F}_{3/2}\right)$ and ${\text{Yb}}^{3+}$ $\left({{}^{2}F}_{5/2}\right)$ excited levels. The energy transfer microparameters for ${\text{Nd}}^{3+}\to {\text{Yb}}^{3+}$ forward and back energy transfers are estimated from the spectral data analysis. A parameter, ${\Phi }_{\text{ET}}$ $\left(=C_{DA}^{\text{Nd-Yb}}/C_{DA}^{\text{Nd-Nd}}\right)$, is proposed as a quantitative measure of sensitization ability per unit loss of the donor. The parameter is found to be highest for the presently reported barium-alumino-metaphosphate glasses.