A series of novel 1H-dibenzo[a,c]carbazole derivatives were synthesized in good yield through reaction of methyl 7-oxo-dehydroabietate with a variety of substituted phenylhydrazines. The structures of the newly synthesized compounds were confirmed by IR, (1)H NMR, MS spectral studies and elemental analysis. All compounds were investigated for their activity against four bacteria (Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescens) and three fungi (Trichophyton rubrum, Candida albicans and Aspergillus niger). Among the compound tested, 6d, 6e, 6f and 6m exhibited pronounced antibacterial activities and 6e and 6m also showed moderate antifungal activities. Particularly, 6d exhibited stronger antibacterial activity against B. subtilis comparable to positive control.