Spontaneous emission spectra of wurtzite (WZ) InxGa1−xN/GaN quantum wires (QWRs) with screening effects are investigated as a function of an In content and a carrier density. The screening potentials rapidly increase with increasing carrier density. However, for a given carrier density, the magnitude of the screening potential is nearly irrespective of the In content. In the case of the InGaN/GaN quantum well (QW) structures, the peak intensity gradually decreases with increasing In content owing to the increase in an internal field by piezoelectric (PZ) and spontaneous (SP) polarizations. On the other hand, the peak intensity of the InGaN/GaN QWR structure is less sensitive to an internal field and rapidly increases owing to the increase in the carrier confinement with increasing In content. However, it is reduced due to the decrease in a quasi-Fermi level separation when the In content further increases.