Multisystem inflammatory syndrome is a life-threatening condition associated with elevated inflammatory markers and multiple organ injury. A diagnosis of exclusion, it has been reported after severe acute respiratory syndrome coronavirus 2 infection (SARS-CoV-2) in children and adults; recently it has been described in some post-COVID-19 vaccinated individuals. The prognosis with supportive care and immunomodulatory therapy is good, although some individuals may require treatment in the intensive care unit (ICU). Here we report a case of a 58-year-old man who developed multi-organ failure after receiving the second dose of the Moderna mRNA-1273 COVID-19 vaccine. He required critical organ support in the ICU. An extensive workup was done to rule out alternative infectious and inflammatory processes. Following a period of gradual in-hospital convalescence, our patient made a full recovery. To our knowledge, this is the first comprehensively described case of multisystem inflammatory syndrome associated with Moderna mRNA-1273 COVID-19 vaccine in an adult over 50 years of age.