We report in this work the synthesis, cytotoxicity, and antimicrobial activity of ([1,2,4]triazolo[1,5-c]quinazolin-2-ylthio)carboxylic acid amides 4-7 in connection with our previous research in the preparation of triazoloquinazoline derivatives. Due to simplicity, general availability of starting materials, and high yields, the most reliable method of synthesis appeared to be the one with N,N-carbonyldiimidazole activation stage. The chemical structures of all obtained substances were deduced from FT-IR, (1)H-NMR, EI-MS, and LC-MS spectral data. The results of cytotoxicity evaluated by bioluminescence inhibition of bacterium Photobacterium leiognathi, strain Sh1 showed that compounds 4.1, 4.6, and 6.1 were the most cytotoxic. Investigation of the antimicrobial and antifungal activity of amides 4-7 (concentration 5 mg/mL) was carried out by the stiff-plate agar-diffusion method. We found that the compounds possessed low (4.1, 4.7) antifungal activity against Candida tenuis and strong (4.21, 5.1, 5.9) or inefficient (4.7, 4.12, 4.16) activity against Aspergillus niger. Substances 5.1 and 5.9 slightly affected Mycobacterium luteum. Staphylococcus aureus was resistant to all obtained substances, and only the n-butyramide derivatives 7.1 and 7.5 inhibited the growth of Escherichia coli. Hence, there was no strong correlation between bioluminescence inhibition and antimicrobial activity of the investigated substances.