The series of novel N-aryl(alkaryl)-2-[(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazoline-6-yl)thio]acetamides were obtained by aminolysis of activated acids 1a–1d and by alkylation of potassium salts 2a–2d by N-aryl-2-chloroacetamides. The structures of compounds were determined by IR, 1H, 13C NMR, LC- and EI-MS analyses. The results of cytotoxicity evaluation by bioluminescence inhibition of bacterium Photobacterium leiognathi Sh1 showed that compounds reveal moderate cytotoxicity. Screening of anticancer activity in vitro yielded the most active compounds 3t, 4b, 4f, 4l and 4n in micromolar concentrations with the GI50 level (logGI50 is from -7.57 to -4.05 for different cell lines, and logGI50 mean graph midpoint varied from -5.30 to -4.50). Moreover, compound 4b had a distinctive selectivity against renal cancer, 4f—colon cancer and melanoma and 4l—renal cancer. The highest sensitivity to compound 4b showed renal cancer cell lines A498 (logGI50 = -7.57). SAR-analysis was discussed, COMPARE analysis and docking was studied.