Necrotizing fasciitis (NF) is a rare complication of varicella zoster (chicken pox) infection. Its diagnosis can be delayed or missed, which increases mortality and morbidity, because it initially presents similarly to cellulitis. We present the case of a 5-year-old boy who presented with a swollen leg, the difficulties in the diagnosis of NF, and a review of the literature. Necrotizing fasciitis complicating varicella zoster in children is associated with 3.4% mortality, although this rises to 13.6% in streptococcal toxic shock syndrome. Seventy-one percent of cases are confirmed as being caused by group A β-hemolytic Streptococcus. The association of NF with chicken pox is discussed along with the difficulties in diagnosis and treatment options. Necrotizing fasciitis is a surgical emergency and should be considered by all emergency department acute care practitioners in cases of varicella in which fever is enduring and swelling or pain is disproportionate. Because of the difficulty in diagnosis, senior opinion should be sought early.