The flight from Dublin to Krakow made the unexpected diversion after a reported bomb threat, German newspaper Bild Zeitung said.
With 160 people on board, the flight arrived at the Berlin-Brandenburg airport shortly after 8 pm (1800 GMT) Sunday, remaining on the tarmac into early Monday morning.
A Berlin police spokesperson said that officers had completed their security checks "without any danger being detected".
"The passengers will resume their journey to Poland on board a spare aeroplane," she told AFP, without giving more precise details for the alert.
The flight was emptied with the baggage also searched, German media reported.
"The Ryanair plane that made an emergency landed reported an air emergency and was therefore immediately given a landing permit at BER," airport spokesman Jan-Peter Haack told Bild.
"The aircraft is currently in a safe position," a spokeswoman for the police told the newspaper.
The incident comes a week after a Ryanair flight was forced to divert to Belarus, with a passenger -- a dissident journalist -- arrested on arrival.
And in July last year, another Ryanair plane from Dublin to Krakow was forced to make an emergency landing in London after a false bomb threat.