Novel thiadiazole derivatives bearing hydrazone moieties were synthesized through the reaction of 2-[(5-methyl-1,3,4-thiadiazol-2-yl)thio)]acetohydrazide with aldehydes/ketones. The chemical structures of the compounds were elucidated by (1)H-NMR, (13)C-NMR, MS-FAB spectral data, and elemental analyses. Behavioral effects of the test compounds in mice were examined by hole-board, activity cage, tail suspension and modified forced swimming tests (MFST). Antinociceptive activities were evaluated using the hot-plate and tail-clip methods. Results of the experiments indicated that the test compounds did not significantly change the exploratory behaviors or locomotor activities of animals in the hole-board and activity cage tests, respectively. Administration of the reference drug fluoxetine (10 mg/kg) and compounds 3a, 3b, 3c, 3j, 3k, and 3l significantly shortened the immobility times of animals in the tail suspension and MFST tests, indicating the antidepressant-like effects of these derivatives. Morphine (10 mg/kg) and compounds 3a, 3b, 3c, 3d, 3e, 3j, 3k, and 3l increased the reaction times of mice in both the hot-plate and tail-clip tests, indicating the antinociceptive effects of these compounds. To the best of our knowledge, this is the first study of central nervous system activities of chemical compounds carrying thiadiazole and hydrazone moieties together on their structures.