Septic arthritis usually affects native joints and represents an invasion of the joint space by a wide variety of microorganisms, most commonly bacteria, such as Staphylococci, Streptococci, and Gram-negative rods. An extremely rare case of septic knee arthritis caused by Pantoea agglomerans in a 67-year-old male is presented. The patient was initially treated with arthroscopic debridement, but due to persistent symptomatology open surgical debridement 3 days after initial surgery was also performed. Cultures yielded P. agglomerans and Streptococcus agalactiae. He was commenced on causative antimicrobial treatment including intravenous linezolid, ciprofloxacin, and clindamycin. He was discharged 10 days later, on oral linezolid and ciprofloxacin for 3 months. Delayed diagnosis in septic arthritis cases and inadequate control of the infection may lead to insufficient treatment and devastating consequences for the patient. The treatment includes surgical debridement and proper antimicrobial agents. Cultures dictate the proper treatment; hence, microbiological examination is of utmost importance, since it may reveal unusual organisms for which empirical treatment may prove insufficient.