Necrotizing fasciitis (NF) is a rare, life-threatening soft tissue infection that affects the skin, subcutaneous tissue, fascia, and muscle, and is characterized by rapid spread and invasion of pathogens. Treatment is possible with early diagnosis, appropriate antibiotic therapy, and quick surgical intervention. Nevertheless, despite all interventions, it is sometimes difficult to manage NF. The Authors present the case of a patient with extensive NF caused by multidrug-resistant Acinetobacter baumannii (A. baumannii) that developed following an intramuscular injection of diclofenac sodium administered at home by someone who was not a healthcare professional. Wound sample culture revealed multidrug-resistant A. baumannii. The patient was treated using negative-pressure wound therapy along with antibiotic treatment and extensive surgical debridement.