In this work synthesized a new series of pyrazoline compounds containing azo linkages via classical and one pot three component reactions. The progress started with 3-chloro,4-methyl aniline which has been diazotized and coupled with 4-hydroxy acetophenone to form azo compound 1-(3-((3-chloro-4-methylphenyl) diazenyl)-4-hydroxyphenyl) ethan-1-one (1) and converted to 1-(4-(benzyloxy)-3-((3-chloro-4-methylphenyl) diazenyl) phenyl) ethan-1-one (2). The later azo compound subjected to both classical and one pot method to give target pyrazoline derivatives. The structure of all new obtained compounds were supported by spectral data (1H-NMR, 13CNMR, Dept.135, and FT-IR). Finally, some pyrazoline derivatives were estimated for their anti-bacterial activity against Escherichia coli as gram negative and Staphylococcus aureus as gram positive. The results showed significant activity against both types of bacteria.