Triazines are in great interest for their potential to mimic nucleoside analog compounds. Three different isomers exist including 1,2,3-triazine, 1,3,5-triazine (s-triazine) and 1,2,4-triazine. All of these skeletons were investigated. Among them, 5,6-diaryltriazines were previously tested on MCF7 and other tumor cell lines. In this study, we have synthesized and characterized 9 novel 5,6-diaryl-1,2,4-triazine derivatives (4a-i) using ¹HNMR, ¹³CNMR, and HRMS spectra. Contributing to the previous data, we tested our compounds on U87MG, C6 and SH-SY5Y cell lines along with MCF7. We evaluated if these compounds affect CNS tumors in vitro, which cell lines have different protein profiles from MCF7 and mainly nucleosides are used as their antiproliferative agents. Briefly, compounds showed good antitumor activity on the C6 cell line with up to 50% inhibition for 7 of 9 compounds (4b, 4d–i) at 50 μM. Additionally, compounds showed moderate activity on U87MG glioblastomas, compound 4a was the most active with 29.68 μM IC₅₀. Compounds did not show significant activity on SH-SY5Y cells. Cytotoxicity evaluation gave the results that the synthesized compounds show moderate cytotoxicity on NIH-3T3 and severe cytotoxicity on HEK 293. The study leads the investigations of triazines with glioma cell lines.