Group C underdogs Poland missed a chance to take an early lead when forward Arkadiusz Milik hit the crossbar following a pass by striker Robert Lewandowski.
Cheered on by a capacity crowd of over 41,000 in the Baltic city of Gdansk, the Polish defence failed to stop Steven Berghuis's pass finding the head of the Dutch league's leading scorer Janssen who opened the scoring in the 33rd minute.
The Netherlands, who failed to qualify for Euro 2016, dominated the first half with Jetro Willems and Quincy Promes causing problems for the hosts.
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Poland started the second half more brightly, despite a lacklustre performance by Bundesliga leading scorer Lewandowski, but they needed a set piece to level the scores, with left back Artur Jedrzejczyk heading in Milik's corner in the 60th minute.
With Dutch fans waving a conciliatory banner reading "Good luck in France, we stay at home", Wijnaldum chipped the ball into the net from a Luciano Narsingh pass in the 76th minute.
Poland were without Sevilla midfielder Grzegorz Krychowiak, who is recuperating from a knee injury, but is set to be fit for the European Championship which starts on June 10.
Poland are in Group C along with traditional rivals Germany, Ukraine and Northern Ireland.
Knocked out in the pool stage when they co-hosted the tournament four years ago with Ukraine, Poland play Lithuania in their last warm-up friendly on Monday before their opening group game against Northern Ireland on June 12.
(Reporting by Adrian Krajewski, editing by Ed Osmond)
