Background: Vertebral osteomyelitis caused by Stenotrophomonas maltophilia is very rare. There are only two cases reported in literature. Here, we present a 48-year-old immunocompetent male who, following a lumbar microdiscectomy, developed postoperative spondylodiscitis due to S. maltophilia that mimicked a cotton granuloma. Case Report: Two months ago, a 48-year-old male underwent a lumbar L4-L5 microdiscectomy, he newly presented with the left thigh and leg pain of 4 weeks duration. Laboratory studies revealed a CRP of 26 mg/l, an ESR of 6 mm (1 st h), and total leukocyte count of 7.85 thousand/ul. The MRI T2 images showed a focal hyperintense lesion in the left lateral recesses at the L4-L5 level; the accompanying hypointense-smooth margin resembled a cotton granuloma. At surgery, we found a localized epidural collection of pus; S. maltophilia was isolated from the culture. His symptoms gradually improved, and symptoms fully resolved with 3 months of subsequent antibiotic therapy. Conclusion: S. maltophilia causing vertebral osteomyelitis is extremely rare and can sometimes mimic a cotton granuloma. MR diagnosis, surgical decompression, and obtaining cultures are requisite to direct appropriate antibiotic therapy.