Poznan is located halfway between Berlin and Warsaw and can be reached by train from either city or by plane from Frankfurt, London Stansted, Munich or Warsaw every day and less frequently from Barcelona, Bristol, Bourgas, Cork, Dortmund, Doncaster/Sheffield, Dublin, Edinburgh, Glasgow/Prestwick, Copenhagen, Cracow, London Luton, Liverpool, Milano/Bergamo, Oslo Torop/Sanderfjord, Rome Fiumicino, Stockholm Vasteras.
From Warsaw Airport take taxi to Warsaw Central Railway Station ("Warszawa Centralna"). It is safe to take a "Radio Taxi" from the line outside the airport terminal. There is a dispatcher who will call one for you. Reject any offer of taxi from individuals approaching you when leaving the terminal. Trains to Poznan leave the Warsaw Central Station approximately every hour during the day. The ride Warsaw-Poznan takes about 3 hours by express train. For IC (Intercity), EC (Eurocity) and EX (Express) trains a seat reservation is required. You may buy the ticket and seat reservation at the station. For timetable and more information see: PKP SA and Intercity.
There are two airports (Tegel and Schönefeld) in Berlin and you can catch all direct trains to Poznan at Berlin Hauptbahnhof (Main Station) or Berlin Ostbahnhof.
International trains need approximately 3 hours to get to Poznan from Berlin.