We report a case of catheter-related bacteremia due to Tsukamurella pulmonis. T. pulmonis is a rare cause of opportunistic infection in immunosuppressed patients and in cases of indwelling foreign materials. This infection was nearly impossible to identify using conventional phenotyping methods because of its similarities to the related genera Nocardia, Rhodococcus, Gordonia, Streptomyces, Corynebacterium, and Mycobacterium. This organism was initially misidentified as Mycobacterium aubagnense through PCR-RFLP analysis. We correctly identified this organism using 16S rRNA sequencing combined with phenotyping tests. (Korean J Clin Microbiol 2010;13: 93-97)