While Toxoplasma gondii is able to infect and replicate within all eukaryotic cells, tachyzoites are the infective form of T. gondii that invades all eukaryotic cells leading to tissue rupture, the main features of toxoplasmosis. The present study evaluates the activity of (benzaldehyde)-4-phenyl-3-thiosemicarbazone and (benzaldehyde)-(4 or 1) phenylsemicarbazone against intracellular T. gondii. The nine new compounds were incubated in infected Vero cells at concentrations of 0.01, 0.1, 0.5, and 1.0 mM and evaluated for three main effects: cytotoxicity, infection, and number of intracellular parasites. The cytotoxicity test showed a pattern by analyzing the substituent arylhydrazone, where trihydroxy Compounds 4–9 were cytotoxic at concentrations of 0.5 and 1.0 mM. The results highlight Compound 8, which reduced the number of intracellular parasites by 82 % in a concentration of 0.01 mM and showed a LD50 of 0.3 mM in cell culture. These different biological actions are due to changes in the molecular structure and type of radical present in each compound. All compounds tested were more efficient than the control drug sulfadizine.