Multiple myeloma (MM) has been suggested to be associated with different neoplasms. Of 589 consecutive patients with MM, 59 (10%) had different neoplasms: solid tumors in 78% and hematological neoplasms in 22%. Different neoplasms were separated into those emerging prior or synchronously (p/s; n = 41) versus subsequently after the MM (n = 18). The rate of different neoplasms at the time of MM diagnosis was estimated as 6.6%, and estimated different neoplasm rates at 2, 5, and 10 years were 7.8%, 10.3%, and 11.6%, respectively. Patients with MM with p/s different neoplasms showed a hazard ratio (HR) for impaired overall survival of 1.2 (95% CI 0.8-2.0), whereas in those with subsequent neoplasms the HR was 2.5 (95% CI 1.4-4.4). This demonstrates that (1) p/s are more frequent compared with subsequent different neoplasms, and (2) the prognosis is more impaired with subsequent different neoplasms. Age ≥60 years was a confounding covariable with a HR of 2.021 (95% CI 1.6-2.6).