Several CdTe/ZnTe strained single quantum well structures with widths ranging from 5 to 20 Å were grown on GaAs (100) substrates by double-well temperature-gradient vapor-transport deposition. Photoluminescence (PL) measurements on the strained single quantum-well structures showed that the sharp excitonic peaks corresponding to the transitions from the first electronic subband to the first heavy-hole band (E1–HH1) below the critical thickness of the CdTe well were shifted to lower energy with increasing well width. However, the results of the PL spectra above the critical thickness of the CdTe clearly showed broad excitonic peaks, originating from the dislocations in the CdTe quantum well, corresponding to the (E1–HH1) transitions. Electronic subband energies were calculated by an envelope function approximation taking into account the strain effects, and the transition values were in good agreement with those obtained from the experimental measurements.