Chromone-3-phenylcarboxamides (<b>Crom-1</b> and <b>Crom-2</b>) were identified as potent, selective, and reversible inhibitors of human monoamine oxidase B (<i>h</i>MAO-B). Since they exhibit some absorption, distribution, metabolism, and excretion (ADME)-toxicity liabilities, new derivatives were synthesized to map the chemical structural features that compose the pharmacophore, a process vital for lead optimization. Structure-activity relationship data, supported by molecular docking studies, provided a rationale for the contribution of the heterocycle's rigidity, the carbonyl group, and the benzopyran heteroatom for <i>h</i>MAO-B inhibitory activity. From the study, <i>N</i>-(3-chlorophenyl)-4<i>H</i>-thiochromone-3-carboxamide (<b>31</b>) (<i>h</i>MAO-B IC<sub>50</sub> = 1.52 ± 0.15 nM) emerged as a reversible tight binding inhibitor with an improved pharmacological profile. In <i>in vitro</i> ADME-toxicity studies, compound <b>31</b> showed a safe cytotoxicity profile in Caco-2, SH-SY5Y, HUVEC, HEK-293, and MCF-7 cells, did not present cardiotoxic effects, and did not affect P-gp transport activity. Compound <b>31</b> also protected SH-SY5Y cells from iron(III)-induced damage. Collectively, these studies highlighted compound <b>31</b> as the first-in-class and a suitable candidate for <i>in vivo</i> preclinical investigation.