Nineteen new [6‐(4‐methoxyphenyl)‐3(2H)‐pyridazinone‐2‐yl]‐acetamide (1—10) and 3‐[6‐(4‐methoxyphenyl)‐3(2H)‐pyridazinone‐2‐yl]propanamide (11—19) derivatives have been synthesized in this study. The structures of the compounds have been elucidated by their IR and NMR spectral data and elemental analysis. Antinociceptive activity of the compounds has been investigated by modified Koster's Test in mice