Multisystem inflammatory syndrome (MIS) is a new and rare complication of COVID-19 that usually occurs in children. An increasing number of cases of MIS in adults are described in the literature. The condition is associated with high mortality, and treatment is non-standardized. Clinical pictures are heterogeneous, and diagnosis is very challenging. Here we describe a case of MIS in a 60-year-old man with previous follicular lymphoma treated with obinutuzumab and recent SARS-CoV-2 infections. He complained of an unknown fever and developed pancytopenia during the hospitalization, associated with a general clinical worsening. The patient was successfully treated with intravenous immunoglobulin and steroids.