Microbiology rounds are an integral part of infectious disease consultation service. During microbiology rounds, we highlight microbiology principles using vignettes. We created case-based, interactive, microbiology online modules similar to the vignettes presented during microbiology rounds. Since internal medicine residents rotating on our infectious disease elective have limited time to participate in rounds and learn microbiology, our objective was to evaluate the use of the microbiology online modules by internal medicine residents. We asked residents to complete 10 of 25 online modules during their infectious disease elective. We evaluated which modules they chose and the change in their knowledge level. Forty-six internal medicine residents completed assessments given before and after accessing the modules with an average of 11/20 (range, 6 to 19) and 16/20 (range, 9 to 20) correct questions, respectively (average improvement, 5 questions; P = 0.0001). The modules accessed by more than 30 residents included those related to Clostridium difficile, anaerobes, Candida spp., Streptococcus pneumoniae, influenza, Mycobacterium tuberculosis, and Neisseria meningitidis. We demonstrated improved microbiology knowledge after completion of the online modules. This improvement may not be solely attributed to completing the online modules, as fellows and faculty may have provided additional microbiology education during the rotation.