New organotin (IV) based on 2-(thiophene-2-yl)acetic acid and 1-H-pyrazole-3-carboxylic acid derivatives 1-ae and 2a-e was prepared and characterized by IR, 1H and 13C NMR spectroscopy. These reactions were carried out under refluxing conditions using CHCl3 / EtOH (3:1) as solvents and 2:1 / 1:1 acid / metal oxide rations. The tin products were recuperated with moderate and good yields (55-85%). The Compounds (1b, 1e and 2e) were screened for their antitumor activities against two human tumor cell lines: HeLa, an epithelial cell from a fatal cervical carcinoma and HEK293, an embryonic kidney tumor. All three materials show an activity in vitro against these cell lines.