Russian Dmitri Shoukov gave the home side the lead after 17 minutes, but Ignacio Tuhuteru gave Groningen hope when he put Dwight Lodegewes's side back on level terms with a goal just before half time.
Groningen put up a spirited performance, but could not hold Willem out and Dutch international Denny Landzaat (pictured) grabbed the crucial second from the penalty spot after 63 minutes.
Landzaat then wrapped up the win with a goal 11 minutes from time.
Groningen remain second from bottom, but all their rivals have at least two games in hand - Willem remain in 9th place.
Click below for match summary:
Willem II v Groningen
