Objective: Shin'iseihaito (Xin yi qing fei tang in Chinese, SSHT), a formula in traditional Japanese Kampo medicine and Chinese medicine comprising nine crude drugs, Gypsum, Ophiopogon Tuber, Scutellaria Root (SR, root of Scutellaria baicalensis), Gardenia Fruit, Anemarrhena Rhizome, Lilium Bulb, Magnolia Flower, Loquat Leaf, and Cimicifuga Rhizome, is commonly used to treat sinusitis associated with purulent nasal discharge and reddish nasal mucosa. We evaluated anti-bacterial activity of SSHT extract on Streptococcus pneumoniae, the major cause of bacterial sinusitis. Materials and Methods: Sterile paper disks impregnated with SSHT extract or each extract of its component were placed on sheep blood agar plates inoculated with Streptococcus pneumoniae (ATCC 49619). The diameter of inhibitory zone was measured after 20-24 h incubation. Results: SSHT extract and each water extract of Ophiopogon Tuber, SR, Gardenia Fruit, Anemarrhena Rhizome, Lilium Bulb, Magnolia Flower, and Cimicifuga Rhizome showed significant antibacterial activity against Streptococcus pneumoniae, and SR extract exhibited the largest inhibitory zone. SR extract was partitioned into AcOEt, BuOH, and water layer, and water layer was further separated into 80% EtOH soluble and insoluble fraction. Among them, only 80% EtOH soluble fraction was exhibited antibacterial activity. In this fraction, we found baicalin as the major compounds, and baicalin exhibited antibacterial activity against Streptococcus pneumoniae in concentration-dependent manner. Conclusion: SSHT has antibacterial activity against Streptococcus pneumoniae, and SR and its major constituent baicalin contribute to the antibacterial activity of SSHT against Streptococcus pneumoniae.