As part of our search for searching for anticancer agents a novel series of thieno [2, 3-d] pyrimidine derivatives 9-14 were obtained via reaction of the strategic starting material ethyl 2-isothiocyanato-4, 5-dimethylthiophene-3- carboxylate 2 with sulfa-drugs namely, sulfanilamide, sulfa-thiazole, sulfa-diazine, sulfa-merazine, sulfa-dimethoxazine and sulfa- doxine, in dimethylformamide containing triethylamine as catalyst. The structures of the newly synthesized compounds were established by microanalysis, IR, 1H-NMR, 13C-NMR and mass spectral data. All the newly synthesized compounds were evaluated for their in vitro anticancer activity against human breast cancer cell line (MCF7). Most of the screened compounds exhibited higher anti-breast cancer activity compared with Doxorubicin as a reference drug. Compounds 14, 13, 9 and 12 (IC50 values 22.12, 22.52, 27.83 and 29.22 μM) showed higher anti-breast cancer activity than the Doxorubicin as a reference drug with (IC50 value 30.40 μM). In addition, compounds 10 and 11 with (IC50 values 34.64, 37.78 μM) are nearly as active as Doxorubicin as positive control.