Synthesis, characterization, antioxidant and antimicrobial activities of novel pyrazolines and phenylpyrazoline containing substituted pyridine and piperazine benzoisothiazole moieties have been reported. When these synthesized compounds were exposed for antioxidant screening, some among them exhibited prominent DPPH radical scavenging activity and superoxide radical (SOR) scavenging activity where ascorbic acid used as standard. During the antimicrobial screening compounds, some derivatives were found to be very active against Cryptococcus neoformans, which was supported on the basis of higher free binding energies with methionyl-tRNA synthetase.