Urinary tract infections (UTIs) are caused primarily by uropathogenic Escherichia coli (UPEC), which encode filamentous surface-adhesive organelles called type 1 pili. FimH is located at the tips of these pili. The initial attachment of UPEC to host cells is mediated by the interaction of the carbohydrate recognition domain (CRD) of FimH with oligomannosides on urothelial cells. Blocking these lectins with carbohydrates or analogues thereof prevents bacterial adhesion to host cells and therefore offers a potential therapeutic approach for prevention and/or treatment of UTIs. Although numerous FimH antagonists have been developed so far, few of them meet the requirement for clinical application due to poor pharmacokinetics. Additionally, the binding mode of an antagonist to the CRD of FimH can switch from an in-docking mode to an out-docking mode, depending on the structure of the antagonist. In this communication, biphenyl α-D-mannosides were modified to improve their binding affinity, to explore their binding mode, and to optimize their pharmacokinetic properties. The inhibitory potential of the FimH antagonists was measured in a cell-free competitive binding assay, a cell-based flow cytometry assay, and by isothermal titration calorimetry. Furthermore, pharmacokinetic properties such as log D, solubility, and membrane permeation were analyzed. As a result, a structure–activity and structure–property relationships were established for a series of biphenyl α-D-mannosides.