Lemierre's syndrome (LS) is a rare life-threatening infective condition typically starting with an oropharyngeal infection causing thrombophlebitis and metastatic abscesses. The most common aetiology of LS is Fusobacterium necrophorum; however, it can also occur after infection with other organisms. LS mainly affects young healthy adults. The initial infection site can be in the head and neck or in the abdomen. The morbidity rate of this disease is high despite aggressive treatments. In this article, we report a 63-year-old male patient with uncontrolled diabetes mellitus, presenting with Klebsiella pneumoniae infection-induced necrotizing fasciitis on the right side of the neck, leading to LS.