Compound 4, 5, 6, 7, and 8 were synthesized from 4-benzoyl-1,5-diphenyl-1H-pyrazole- 3-carboxylic acid 1 as a starting material. The pyrazolo[ 4,3-d] oxazinone 4 was obtained from direct reaction of the acid 1 with hydroxylamine hydrochloride. Acid chloride 2 was converted easily into the new derivatives consisting of 1-(4-benzoyl-1,5-diphenyl-1H-pyrazol-3-oyl)-sulfamide 5 and 3,4-dibenzoyl-1,5-diphenyl-1H-pyrazole 6. The nitrile derivative 7 was obtained by dehydration of the amide 3 in a mixture of SOCl2 and Dimethylformamide (DMF). Cyclocondensation reaction of 7 with anhydrous hydrazine led to the formation of 7-aminopyrazolo[ 3,4-d] pyridazine 8 derivative. These new synthesized compounds evaluated for their antibacterial activities against Gram-positive and Gram-negative bacteria using the tube dilution method. The finding of antibacterial activity study showed that the sulfamide derivative 5 was the best compound of the series, exhibiting antibacterial activity against both Gram-positive and Gram-negative bacteria.