Some novel derivatives of 2‐alkyl 6‐substituted pyridazin‐3(2H)‐ones were synthesized by condensation of 3,6‐dichloropyridazine with the sodium salt of benzyl cyanide, followed by hydrolysis and coupling with alkyl halides. The synthesized compounds were screened as cyclooxygenase (COX)‐1/COX‐2 inhibitors and as analgesic and anti‐inflammatory agents. Among the synthesized compounds, 6‐benzyl‐2‐methylpyridazin‐3(2H)‐one (4a), 6‐benzoyl‐2‐propylpyridazin‐3(2H)‐one (8b), and 6‐(hydroxy(phenyl)methyl)‐2‐methylpyridazin‐3(2H)‐one (9a) displayed the highest COX‐2 selectivity indices of 96, 99, and 98, respectively, and analgesic efficacies of 47%, 46%, and 45% protection, respectively. Also, compounds 4a, 8b, and 9a showed anti‐inflammatory activities of 65%, 60%, and 62% inhibition of edema, respectively, at a dose of 10 mg/kg, which is higher than that of diclofenac (58% inhibition of edema).