Injection site abscess is an iatrogenic infection. Intramuscular (IM) injection is a common route to administer medication. Microorganisms known to cause injection site abscess are Staphylococcus aureus, Pseudomonas, Klebsiella, Escherichia coli commonly, Atypical mycobacteria, Clostridium species rarely. Gas gangrene is a necrotic infection of soft tissue with high mortality, often necessitating amputation in order to control the infection. Here, presenting a case of gas gangrene in a 19-year-old healthy male, who developed a life-threatening infection after IM injection of sodium diclofenac. Prompt clinical diagnosis, laboratory support, and timely surgical intervention saved the patient's life.