In this study, a novel series of 2-(4-substituted piperazin-l-ylmethyl)-6-(thien-2-yl)-2H-pyridazin-3-ones (3a-f), 2-(4-substituted piperazin-l-ylcarbonylmethyl)-6-(thien-2-yl)-2H-pyridazin-3-ones (4a-c) and 2-[2-(4-substituted piperazin-l-ylcarbonylethyl)]-6-(thien-2-yl)-2H-pyridazin-3-ones (5a,b) were prepared from 6-(thien-2-yl)-2H- pyridazin-3-one (1). In addition, 3-(4-substituted piperazin-l-ylcarbonyl methyl thio)-6-(thien-2-yl) pyridazines (6a-c) and 3-[2-(4-substitutedpip-erazin-l-ylcarbonyl ethylthio]-6-(thien-2-yl) pyridazines (7a,b) were synthesized. Furthermore, 5-(4-substituted piperazin-l-ylmethyl)-6-(thien-2-yl)-2H-pyridazin-3-ones (12a,b) were prepared. The structures of the new compounds were confirmed by elemental analysis as well as by $^{1}H-NMR$, IR and MS data. Some of the newly prepared compounds were subjected to evaluation for their anti-inflammatory activity against carrageenan-induced paw edema at a dose of 10 mg/kg using indomethacin as the reference standard.