Witt had a disciplinary hearing with NHL's senior vice-president and director of hockey operations, Colin Campbell on Friday.
"We are disappointed to lose a player of Brendan's calibre and character for this period of time," Islanders' GM Garth Snow said in a statement. "But we understand the league's concerns regarding hits to the head."
The incident happened in the third period of the Maple Leafs' 5-4 shootout win over the Islanders.
Witt was assessed a 5-minute major and a game misconduct on the play.
The veteran defenceman has seven assists and a minus-31 over his 49 games with the Islanders this season.
He will lose $74,372.75 in salary over the course of the five game ban. Witt would be available to return in time for the Islanders' game against the Maple Leafs in Toronto on March 10.
On Friday, Maple Leafs head coach Ron Wilson said Hagman would be sent back to Toronto and not play on Saturday in Ottawa against the Senators.