A 62-year-old immunocompetent woman was admitted with cytomegalovirus (CMV) infection, pulmonary embolism, splenic vein thrombosis and monoclonal gammopathy of undetermined significance (MGUS). Anticoagulation therapy was started. Two months later, seroconversion of CMV IgM to IgG was observed, while the monoclonal protein was no longer detectable. This suggests a relationship between acute CMV infection, transient MGUS and thrombosis. In accordance with current best practice guidelines for provoked venous thromboembolism (VTE), anticoagulation therapy could be discontinued after 3 months instead of 6 for unprovoked VTE, thereby reducing unnecessary time at risk of bleeding complications. While the relationships between CMV and both MGUS and thrombosis have been described independently, we are first to describe these three conditions occurring simultaneously.Furthermore, we provide a systematic review on the relation between CMV, MGUS and thrombosis.