A series of N-cycloalkenyl-2-acylalkylidene-2,3-dihydro-1,3-benzothiazoles 5a-j, N-cycloalkyl-2-acylalkylidene-2,3-dihydro-1,3-benzothiazoles 8a-e, and N-alkyl-2-acylalkylidene-2,3-dihydro-1,3-benzothiazoles 8f-h, were synthesized and tested for in vitro antibacterial and antifungal activities against four gram-positive and five gram-negative bacteria (Bacillus subtilis 6633, Enterococcus faecalis 29212, Staphylococcus aureus 6538, Staphylococcus aureus 25923, Escherichia coli 25922, Acinetobacter calcoaceticus a1, A. calcoaceticus a2, Pseudomonas aeruginosa 27835, Klebsiella oxytoca 49131), four yeast-like fungi and one fungus (Candida tropicalis 750, C. albicans 14053, C. albicans 10231, Cryptococcus laurentii 18803, and Saccharomyces cerevisiae). Microdilution broth and agar dilution methods were used for antimicrobial tests. The findings obtained showed that some of the tested compounds 5 and 8 were effective against some of the bacterial strains used, whereas, only compounds 8b-g exhibited a moderate antifungal activity against the yeast strains evaluated.