We show that in nontypical ferroelectric substances (having nonperovskite crystalline structure and hence no soft phonon mode) such as ZnO:Li, Be, Mg, the ferroelectricity might appear due to indirect interaction of dipoles, formed by Li, Be, or Mg off-center impurities, via free charge carriers. Our estimations show that the typical semiconducting concentration of the carriers like 1017 cm−3 suffices for effect to occur. We have also shown that the properties of impurity-generated ferroelectricity depend on the difference in the ionic radii of the impurity and host lattice ion as well as on their concentrations. Namely, the growing amount of Li and Be promotes ferroelectricity, while the same for Mg inhibits it. Our calculations of spontaneous polarization and ferroelectric phase transition temperature in the above nontypical ferroelectrics as the functions of concentrations of impurity dipoles and carriers capture well the main peculiarities of all available experimental data.