A 46-year-old woman was urgently admitted to our hospital due to acute renal failure, liver dysfunction, disseminated intravascular coagulation, shock status, and impaired consciousness. About 1 day prior to admission, she developed a high-grade fever, bilateral lower leg pain, and multiple small papules. She was diagnosed with streptococcal toxic shock syndrome (STSS) caused by Streptococcus dysgalactiae subsp. equisimilis (SDSE) associated with acute myeloid leukemia. The emm gene type of the isolated SDSE was shown to be stG2078. Her invasive streptococcal infection resolved with immediate administration of meropenem and continuous hemodiafiltration. However, she died of septic shock caused by multidrug-resistant Pseudomonas aeruginosa one month after admission. Recently, epidemiological studies have shown increasing numbers of invasive SDSE infections, including STSS and necrotizing fasciitis, often among immunocompromised patients. This suggests that hematologists as well as primary care doctors need to be aware of the possibility of the invasive infections caused by SDSE. An influenza-like illness consisting of a fever, lower extremity pain, and diarrhea are common initial symptoms in STSS patients. Awareness of these prodromal symptoms could lead to the early diagnosis of the illness and prompt initiation of antibiotic treatment.