In May 2025, a female giraffe in poor body condition died unexpectedly at a zoo in Henan Province, China. A bacterial strain, designated HN-1, was isolated from the heart, liver, spleen, lungs, and kidneys of the deceased animal. After 24 hours of incubation at 37°C on Luria–Bertani (LB) agar, the colonies appeared round, smooth, pale yellow, translucent, and raised. Gram staining revealed that the isolate was a Gram-positive, rod-shaped, and non-spore-forming bacterium. Based on 16S rRNA gene sequencing, the strain showed more than 99.7% homology with reference sequences of E. mexicanum from various sources in GenBank. The results of the susceptibility test showed that E. mexicanum was susceptible to levofloxacin, clindamycin, chloramphenicol, trimethoprim, rifampicin, tetracycline, minocycline, gentamicin, erythromycin, and doxycycline, but resistant to oxacillin, penicillin, ciprofloxacin, and linezolid. These findings provide valuable insights for the diagnosis and treatment of infections caused by E. mexicanum in giraffes.