The nature of the scalar charmed meson $D_0^{*}(2300)$ remains one of the most intriguing states in hadron spectroscopy. A prominent interpretation is a two-pole structure generated by the coupled channels $D\pi$, $D\eta$, $D_s\bar{K}$, and $D\eta \prime$, in which the lower pole couples mainly to $D\pi$ and the higher pole to $D_s\bar{K}$. Following this picture, we calculate the decay constants of these two poles using the effective Lagrangian approach. The resulting values, $f_{D_0^{*}}^{(lower)}={68.46}_{-1.25}^{+0.93}MeV$ and $f_{D_0^{*}}^{(higher)}={90.51}_{-11.64}^{+5.91}MeV$, are substantially smaller than those predicted by conventional $c\bar{q}$ excited-state scenarios. This difference suggests that decay constants can serve as a sensitive probe to discriminate between different internal structures of the $D_0^{*}(2300)$. As a phenomenological application, we further predict the branching fractions for the Cabibbo-favored decays $B_s\to D_s{D}_0^{*}$, ${\Lambda }_b\to {\Lambda }_c{D}_0^{*}$, and ${\Xi }_b\to {\Xi }_c{D}_0^{*}$ within the factorization approach. These predictions provide crucial tests to validate the two-pole interpretation of the $D_0^{*}(2300)$.