It is the first time in nearly three months that all borders with its European Union neighbors are open.
The border restrictions were lifted from midnight local time (2200 UTC).
Poland had already relaxed controls to the border with Lithuania on Friday.
Poland’s government — along with other EU nations — halted entry to the country in mid-March in a bid to slow the spread of the coronavirus.
The decision hit commuters who regularly cross the Polish-German border particularly hard. An exception was agreed for them later.
The reopening follows a European Commission proposal to have all EU borders within the bloc unhindered by June 15.
Poland’s controls at the borders with Ukraine, Belarus and the Russian exclave Kaliningrad remain in place, while requirements from these countries have been relaxed.
Poland’s new travel rules
Under Poland’s new measures, citizens of non-EU members Russia, Belarus and Ukraine are allowed to enter Poland if they are the spouse or child of a Polish citizen or have a work permit for the country.
Workers from these countries will not need to complete a 14-day quarantine on arrival.
Flights to EU destinations are planned to resume on June 16.
It was not immediately clear when train connections within the EU would restart operations.
Since the border closures, the Eurocity train that linked the Polish and German capital cities Warsaw and Berlin had been rerouted to the northern Polish port town of Szczecin.
Train links to Poland’s non-EU neighbors will remain suspended.
When are other EU countries lifting travel restrictions?
The European Commission has been aiming to coordinate border reopening and lifting of travel restrictions throughout the bloc among its 27 member states.
It proposedJune 15 as the date to get EU borders open, but the relaxation of rules have been far from coordinated.
Germany is due to end land border checks on Monday. Belgium, France and Greece are lifting restrictions for all travel within Europe, from the same date, in line with EU recommendations.
Spain will only lift travel restrictions on July 1, with Portugal saying it will also open its border with Spain on the same day.
kmm/mm (AFP, dpa) (DW)