Moder has signed a three-year contract with Feyenoord which runs out in the summer of 2028. Neither club announced a transfer fee but according to reports, Feyenoord paid a fee between 1.5 and 2 million euros.
The 25-year-old midfielder enjoyed limited playing time at Brighton after recovering from a lengthy knee injury. The 31-time Polish international appeared just seven times in all competition for Brighton this season.
“He has recovered brilliantly from a serious knee injury; he wants to cement his place in the Polish team and it’s understandable he wants to play more games," Brighton manager Fabian Hurzeler said in a club statement.
"On behalf of everyone here, I’d like to thank him for his service to the club. He’s been a top professional to work with, and I wish him all the best for his future.”
Moder came to a total of 71 games played for the Premier League side.
Big club
"It all happened pretty fast," Moder said on Feyenoord's website after his transfer. "I am very excited about this new step; I felt I was ready for it.
"It is a new league for me, a new club, but at the highest level. I've heard only positive stories from guys like Mats Wieffer, Yankuba Minteh and Sebastian Szymanski, too."
At Feyenoord, the versatile Moder had kit number 7 assigned to him which was last worn by fellow former Brighton man Alireza Jahanbakhsh.
"Of course it will take some getting used to playing soccer here, but I hope to show what I have to offer as soon as possible," Moder continued.
"Feyenoord is a big club that competes at the European level every year, so I look forward to being there on that stage as well.
"The next two games against Bayern and Lille will still be as a supporter, but after that hopefully on the field. There is a lot to play for and in the end it is only about one thing: winning as often as possible."
Moder will not make his official Feyenoord debut until next month at the earliest as the Pole is not registered for Feyenoord's Champions League campaign.
