As the 16-day event wrapped up in the southern city of Munich, Oktoberfest chief Josef Schmid told reporters that damp, cool weather had led some 400,000 fewer visitors to attend this year's festival.
The total fell to 5.9 million revellers, the lowest level since 2009.
Schmid said the checks at the frontier to manage a record migrant influx had likely also kept some tourists from neighbouring countries from travelling to Munich, national news agency DPA reported.
Beer consumption fell as well, to 7.3 million litres (1.9 million gallons), or 400,000 large glass mugs fewer than in 2014.
But crime was also down, with police recording nine percent fewer mobilisations this year.
Local authorities were at pains to keep beer-drinking partygoers and refugees apart, particularly at Munich's main railway station where some 20,000 migrants arrived on each of the first two weekends of September.
Police said Sunday their efforts had been successful, after many asylum-seekers were picked up at the border and put on buses and trains to other regions of Germany.
"No disturbances were reported" between refugees and revellers, they said in a statement.
Overwhelmed by a record migrant influx, and seeking to register asylum-seekers as they enter the country, Germany on September 13 temporarily reintroduced border controls.
As a result, German rail operator Deutsche Bahn suspended key services to and from Austria and Hungary.
Europe's top economy is expecting to receive up to one million asylum-seekers this year, five times more than in 2014.
Although Oktoberfest began 205 years ago, this year marked the 182nd edition as the party was cancelled during two world wars, two cholera outbreaks, Napoleon's invasion of Bavaria and the hyperinflation of the 1920s.
The event was originally held in October as the name suggests to celebrate a royal wedding but was brought forward by one month to take advantage of better weather.