2-[3-Methyl-7-(thietanyl-3)-1-ethylxanthinyl-8-thio]acetic acid hydrazide was synthesized in two steps by our improved method. The structures of the synthesized compounds were confirmed by IR and NMR spectroscopic data. The acute toxicity was studied. The LD50 values were 700 mg/kg for outbred albino mice. Tail-suspension tests (TST) and forced swimming tests (FST) found that 2-[3-methyl-7-(thietanyl-3)-1-ethylxanthinyl-8-thio]acetic acid hydrazide exhibited antidepressant activity that was most pronounced at a dose of 12 mg/kg.