Several novel 6-[(hetero)arylamino]thieno[3,2-b]pyridines were prepared by palladium-catalyzed C-N Buchwald-Hartwig coupling of the methyl 3-amino-6-bromothieno[3,2-b]pyridine-2-carboxylate with aryl and heteroarylamines, using different reaction conditions. The antitumoral activity of the di(hetero)arylamines obtained was evaluated against three representative human tumor cell lines, namely breast adenocarcinoma (MCF-7), melanoma (A375-C5), and non-small cell lung cancer (NCI-H460) and some structure-activity relationships were established within each series. The most promising compounds were shown to be a benzothiazole derivative with GI50 3.5-6.9 μM followed by an indole derivative with GI50 13-21 μM.