In Germany, mumps has been notifiable until 2013 only in the five Eastern federal states (EFS) of former East Germany. Due to different immunisation policies until 1990 and varying vaccination coverages thereafter, mumps incidences cannot be extrapolated to the 11 Western federal states (WFS). We studied mumps-related International Classification of Diseases (ICD-10) code diagnoses claimed through statutory health insurances between 2007 and 2011 to estimate countrywide mumps incidences in the outpatient sector, and compared them with case numbers from ambulatory notification data. Overall, 32,330 outpatient mumps cases were claimed. Annual incidence ranged between 9.3/100,000 and 11.8/100,000 and showed a significant decreasing trend. Compared with EFS, mumps incidence in WFS was higher and indicated a shift towards older age groups. Notified outpatient case numbers in EFS were 13-fold lower and from voluntary surveillance during an outbreak in the WFS Bavaria 8-fold lower than from insurance data (n=316 versus n=4,217 and n=238 versus 1,995, respectively). Of all notified cases with available information, 75.4% (EFS) and 57.6% (Bavaria) were unvaccinated; 6.8% (EFS) and 19.3% (Bavaria) required hospitalisation. In Germany, mumps is still endemic despite decades of vaccination, with considerable underreporting in the established notification systems.