Comamonas species are one of the numerous genera and species of the Pseudomonas group. Among Comamonas species, Comamonas testosteroni is a rare cause of infections in immunocompromised individuals. Herein, we present a case to emphasize that C. testosteroni could be a causative agent of bacteremia in immunocompromised patients with a history of neutropenia and to determine antibiotic susceptibility of the strain. Blood culture sample of a 30-year-old female patient, who was admitted to the Hematology Clinic for leukopenia, was transferred to our laboratory and then was loaded into the Bactec 9120 (Becton Dickinson, USA) automated blood culture system. The gram-negative bacillilike, catalase- and oxidase-positive colonies grown in the blood culture were then loaded into an automated identification system VITEK-2 Compact (bioMérieux, France). The strain, which was identified as C. testosteroni, was transferred to the Microbiology Laboratory of Marmara University Pendik Training and Research Hospital for verification using the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS; Bruker Daltonics, Bremen, Germany). Accordingly, we aimed to determine antibiotic susceptibility pattern of C. testosteroni grown in our patient with leukopenia whose immune system was compromised due to spontaneous abortion. Accordingly, C. testosteroni, which was found to be moderately susceptible to ampicillin, was found to be susceptible to amoxicillin/clavulanic acid, piperacillin/tazobactam, cefuroxime, cefoxitin, cefoperazone/ sulbactam, trimethoprim/sulfamethoxazole, amikacin, gentamicin, ciprofloxacin, fosfomycin, imipenem and meropenem but resistant to cefixime and ceftazidime.