Introduction <p>Facultative anaerobic bacteria are the predominant pathogens in postoperative lumbar spine infections, while gram-positive anaerobic cocci, such as <i>Finegoldia magna</i> (<i>F. magna</i>), act as opportunistic pathogens and are among the most virulent. We report an elderly woman who suffered <i>Finegoldia</i> infection after lumbar spine surgery. To the best of our knowledge, this is the first well-documented case in the literature.</p> Case description <p>A 67-year-old female underwent a multi-segmental posterior lumbar interbody fusion surgery for lumbar spinal stenosis. On postoperative day 11, central surgical incision dehiscence was noted, accompanied by wound discharge and lumbar-hip pain. Wound secretions were cultured four times and all tested negative for bacteria. The causative agent was identified as <i>F. magna</i> via targeted next-generation sequencing (tNGS) combined with traditional microbial smear microscopy. After 4 days of piperacillin-tazobactam, the patient developed persistent high fever (39.5℃), prompting a cautious switch to combination therapy with vancomycin and metronidazole, which resolved the infection effectively.</p> Conclusion <p><i>F. magna</i> is an uncommon cause of post-lumbar spine surgery infection, warranting a high index of suspicion for this gram-positive anaerobic coccus. When <i>F. magna</i> infection is encountered, treatment with vancomycin or metronidazole may be considered when antimicrobial susceptibility testing is not available.</p>