Globicatella sanguinis is an unusual pathogen causing bacteremia, meningitis, and urinary tract infection, and can be misidentified as Streptococcus pneumoniae or viridans streptococci due to its colonial morphology. A 76-year-old female patient with hypertension and degenerative arthritis was admitted to the hospital complaining of knee joint pain. Blood culture revealed the presence of Gram-positive cocci, and the isolated organism was equally identified as S. pneumoniae using the MicroScan identification system (Beckman Coulter, USA) and Vitek 2 identification system (bioMérieux, USA). However, the isolate showed optochin resistance based on the optochin disk susceptibility test. The organism was finally confirmed to be G. sanguinis based on 16S rRNA sequencing and hydrogen sulfide production testing. Accurate identification of G. sanguinis isolated from aseptic body fluids including blood is important for appropriate antibiotic selection based on accurate application of interpretative criteria of antimicrobial susceptibility test. (Ann Clin Microbiol 2018;21:40-44)