We have performed the photoluminescence, piezoreflectance and contactless electroreflectance study of a Zn0.88Mg0.12S0.18Se0.82 film, grown by molecular beam epitaxy on a (001) GaAs substrate, near the band edge in the temperature range between 15 and 300 K. The features related to the band-to-band excitonic and defect-related transitions of the material are observed and the nature of these features are discussed. In addition, the parameters that describe the temperature dependence of the interband transition energy and broadening function of the excitonic feature are evaluated.