Display omitted •Quantum biochemistry calculation of the binding energy of SERMS with OHT and RAL.•SERMs-OHT binds more strongly when compared to SERMs-RAL.•Selective estrogen receptor modulators are very effective against breast cancer.•MFCC scheme was used for individual contribution of each amino acid residue. In this work we employed quantum biochemistry methods based on the density functional theory (DFT) model and the MFCC (Molecular Fractionation with Conjugate Caps) scheme to unveil the detailed binding energy features of the tissue-selective synthetic agents SERMs (selective estrogen receptor modulators) 4-hydroxytamoxifen (OHT) and raloxifene (RAL), widely used in the breast cancer treatment, co-crystallized with the estrogen receptor α (ERα). Our theoretical/computational results demonstrated that the total binding energies of OHT and RAL to the ERα ligand-pocket correlate with the experimental binding affinity. Besides, we found that SERMs-OHT binds stronger when compared to SERMs-RAL, confirming experimental data, whose main contributions to the total SERMs-ERα binding energy are due to the amino acid residues in decreasing sequence D351>E542>D538>E353>E423, an important information to understand their binding mechanisms.