Liverpool complete signing of Assaidi
Assaidi, 24, scored 20 goals in 68 appearances for the Dutch first division side last season.
He is new Liverpool manager Brendan Rodgers' third signing since he took charge at Anfield following Swansea City midfielder Joe Allen and Italian striker Fabio Borini from AS Roma.
"I'm very happy to play for this big club," Assaidi said in a statement on Liverpool's official website.
"I had offers from other big clubs but I've been waiting for this moment."
Liverpool begin the new Premier League season at West Bromich Albion on Saturday.