A series of 15 mostly new dialkoxyphosphoryl alkyl and aralkyl isothiocyanates were synthesized using two alternative strategies, and their in vitro antiproliferative activity against several cancer cell lines (including drug resistant) is here demonstrated. The IC50 values measured for the new compounds are within the range of 6.3–21.5 μM, and they are quite similar to the activity of two best and