This paper presents the synthesis and in vitro antimicrobial activity studies of 3,4,5-trisubstituted 4,5-dihydro-1,2,4,5-oxadiazaboroles (4) and 3,5-disubstituted 4,5-dihydro-1,2,4,5-oxadiazaboroles (7). The antimicrobial activities of the compounds were assessed against a panel of microorganisms including Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli, Streptococcus mutans, and Candida albicans. Some of the oxadiazaboroles exhibited fair activities against these microorganisms. The pMIC values of the compounds were first correlated with Hammett polar substituent constant (sigma) and lipophilic constant (pi) and statistically significant correlations were obtained. Additionally, the pMIC values of the compounds were correlated with sigma, pi, and some theoretical descriptors and fair 2D-quantitative structure-activity relationship models with clogP, surface area approx, E (LUMO), A mu, and E (HOMO) as independent variables were obtained. Application of training and test sets to quantitative structure-activity relationship models gave good results. Squared correlation matrix of the theoretical descriptors used in the quantitative structure-activity relationship study showed no correlation between the descriptors.