Ifo said its price expectations index for the coming months stood at 53.5 points in September, up from 48.1 in August.
"Unfortunately, this probably means the wave of inflation isn't about to subside," says Timo Wollmershaeuser, head of forecasts at ifo.
German consumer prices, harmonised to make them comparable with inflation data from other European Union countries (HICP), increased by 10.9% on the year in September. That put inflation at its highest in more than a quarter of a century.
Exports On The Increase
Elsewhere, German exports rose slightly more than expected in August despite a cooling global economy, rising interest rates and material shortages, the country's statistics office said.
Stronger demand from the United States and China helped push exports to €133.1 billion in August, up 1.6% from the previous month.
Imports also increased more than expected, rising 3.4% to €131.9 billion, the seventh month in a row of growth.
A Reuters poll had predicted a month-on-month rise in both exports as well as imports of 1.1%.
Analysts welcomed August's numbers but warned that amid a gloomy economic outlook, exports could become a drag on growth.
High energy costs due to the war in Ukraine are slowing domestic production, which will have a negative effect on exports, said VP bank's head economist Thomas Gitzel.