A series of N-((10-alkyl-10H-phenothiazin-3-yl)methylene)benzohydrazide have been synthesized via condensation of 10-alkyl-10H-phenothiazine-3-carbaldehyde with different heterocyclic acetohydrazides. The reactions were carried out under both conventional and ultrasonic irradiation conditions. In general, improvement in rates and yields were observed when reactions were carried out under sonication compared to classical synthetic conditions. Structures of all the newly synthesized compounds were characterized by IR, 1H NMR, 13C NMR, and mass spectra. Antibacterial activities of the synthesized compounds were studied against bacterial strains Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus, and Klebsiella pneumonia. The free radical scavenging activities of synthesized compounds were screened for in vitro antioxidant activity. © 2013 Springer Science+Business Media Dordrecht.