A new clinical variant of Sweet syndrome, called giant cellulitis-like Sweet syndrome, can masquerade as cellulitis because the patients present with an acute onset of large erythematous plaques, fever, and leukocytosis with neutrophil predominance. This case describes a 90-year-old female with a history of invasive ductal carcinoma of the breast who presented with 3 days of erythema of the right chest and right leg. Physical examination was notable for well-demarcated, blanching erythematous rashes involving the right chest and right lower extremity. Laboratory data was notable for neutrophilic leukocytosis. A clinical diagnosis of cellulitis was made initially, and intravenous cefazolin was initiated. The rash had only partially improved with antibiotics. Skin biopsy revealed a dense neutrophilic infiltrate, which was consistent with Sweet syndrome. Based on the widespread plaques, this case was considered a "giant cellulitis-like" variant of Sweet syndrome. Clinicians should have a high index of suspicion for Sweet syndrome when assessing a patient with fever, neutrophilia and erythematous skin plaques atypical of cellulitis because this condition does not respond to antimicrobial therapy and requires systemic glucocorticoid therapy.