A novel room temperature phosphorescence (RTP) sensor consisting of quantum dots (QDs)-drug nanohybrid was used for the investigation of interaction between epirubicin (EPI) and double-stranded deoxyribonucleic acid (ds-DNA). The method based on the quenching effect of EPI on the phosphorescence emission of Mn-doped ZnS QDs via photoinduced electron-transfer (PIET) mechanism. Adsorption of EPI to the QDs surface caused quenching of RTP emission of QDs via photoinduced electron-transfer process. Whereas, with the addition of DNA provided the restoration of emission due to removing of EPI from the surface. The quantum dots were synthesized in an aqueous medium and characterized. The diameter of prepared QDs were about 3.5 nm, spherical, and uniform size. The quenching mechanism of QDs by EPI is not only collisional but also static. The static and dynamic quenching constants were found as 5.36 x 10(5) M-1 and 3.19 x 10(4) M-1, respectively. In addition to this method, fluorescence and absorption spectrometric methods were used to evaluate DNA/drug interaction and calculate the binding constant (K), which was 3.83x10(5) M-1. Proposed method has advantages such as simplicity and avoids interferences from autofluorescence and scattering light.