In this work, we report the behaviour of isoelectronic oxygen in CdTe studied by photoluminescence measurements. We show that the luminescence occurring at 1.55 eV in CdTe annealed in an oxygen-reach atmosphere can be assigned to oxygen. The luminescence band consists of a zero-phonon line at 1.58 eV, followed by a series of sharp lines due to interaction with the optical and acoustic modes. The fine structure related to the optical modes shows a thermal behaviour different from the structure related with acoustic modes disappearing rapidly after 30 K. The zero-phonon line as well as the LO-phonon replicas exhibit the same temperature dependence exp(-aT 2 ). The half-widths of these replicas increase linearly with the number of emitted phonos.