Twenty-one novel pyrazole azo compounds were synthesized by coupling 3-amino-5-hydroxy-1H-pyrazole and 3-amino-1-phenyl-2-pyrazoline-5-one with diazonium salts derived from aniline, o, m, and p-nitroaniline, o and p-methoxyaniline, o, m, and p-chloroaniline, and o, m, and p-methylaniline. Spectroscopic data for these dyes, dissolved in six solvents, were measured. The effects of acid and base on the visible absorption spectra of the dyes are also reported. The structures of all the compounds were confirmed by Fourier-transform infrared spectroscopy, mass spectroscopy, ultraviolet and visible electronic absorption spectroscopy, nuclear magnetic resonance spectroscopy, and elemental analysis. In addition, the antimicrobial activity of the dyes against six pathogenic bacteria were examined in detail.