[Objective] Oolong tea extract (OTE) was tested for its potential as an electron staining reagent to substitute for uranyl acetate (UA) in electron microscopy of bacterial cells. [Methods] Three electron microscopic staining methods (standard, 0.05% OTE, and 0.1% OTE) were compared for electron microscopic observation of ultrathin sections with or without lead citrate (Pb). First floating the sections on the compared staining solutions for 10?15 min, then if need to post-stained with lead citrate, after rinsing with deionized water three times, the sections were re-floated on lead citrate for 8?10 min. Electron microscopy was performed on sections from LR-White-embedded cells of a Gram-negative bacterium, Escherichia coli, and a Gram-positive bacterium, Staphylococcus aureus. [Results] Both concentrations of the OTE preparations showed the staining results were similar to that of standard method with UA and Pb in E. coli and S. aureus cells. [Conclusion] This study demonstrated that OTE could potentially be used as an alternative to UA in electron microscopy staining for certain structures.