Germans work on average until they are 63, one year more than they did in 2002, figures published by the family ministry showed on Wednesday.
The findings come as the official retirement age is due to increase over coming years from 65 to 67 years to compensate in part for a rapidly ageing population that is living longer.
In 2008, one-third of those aged 60 or older were still working in Europe's biggest economy, the study of elderly people found, an increase of 13 percent from 2002.
German retirement ages were about average among industrialised countries, according to Clemens Tesch-Roemer, head of the group that carried out the study.
People tend to work for longer in Britain, Scandinavian countries or Switzerland, but retire earlier in southern European nations, the data showed.
Family Minister Kristina Schroeder said she expected the trend to continue "because companies cannot allow themselves to let good staff leave" as German demographic pressure increases.
The new retirement age of 67 is only forecast to be reached around 2030.
In neighbouring France, a plan to raise the official retirement age to 62, from 60 at present, has provoked massive street protests by more than one million people.