The low‐temperature photoluminescence (PL) spectra of CuGaS2are investigated in this work. At 4.2 K, high‐quality single crystals grown by both the iodine‐transport and the melt‐growth methods showed many sharp PL lines. Free‐exciton (2.504 eV) and bound‐exciton (2.501, 2.495, and 2.493 eV) lines are studied in detail with respect to transition energy, temperature, and excitation intensity. Phonon‐assisted transitions have been observed in the low‐energy regions of zero‐phonon lines at 2.493, 2.404, and 2.397 eV. Most of them have been well interpreted on the basis of the phonon energies previously obtained by Raman measurements.