Tammy Abraham’s first Swansea goal since he joined on loan from Chelsea and a Jordan Ayew effort gave Paul Clement’s Swansea their first victory of the campaign.
After defeats against Huddersfield Town and Liverpool, De Boer is still waiting for his first point and his first league goal as Palace manager.
The former Netherlands defender was appointed in June after Sam Allardyce retired.
Swansea gave a debut to new signing Sam Clucas and flew out of the traps at Selhurst Park, going close in the fourth minute when Ayew headed just wide from Abraham’s right-wing cross.
James McArthur menaced for Palace, but Swansea remained on top and after Abraham had tested Wayne Hennessey and Alfie Mawson had headed off-target from the ensuing corner, they went ahead in the 44th minute.
An injury to James Tomkins brought Martin Kelly into the Palace defence and he had been on the pitch for less than two minutes when Abraham stole in front of him to volley in Leroy Fer’s cross.
It was Swansea’s first shot on target of the season.
Palace were booed off at half-time and despite De Boer sending on Lee Chung-Yong for Patrick van Aanholt at the break, the home side fell even further behind within three minutes of the restart.
Kelly was once again at fault as he was robbed on halfway by Kyle Naughton, who freed Ayew to round Hennessey and score.
A perfectly timed sliding challenge by Mike van der Hoorn prevented Palace substitute Yohan Cabaye halving the arrears, while Andros Townsend dragged narrowly wide of the Swansea goal late on.
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