Leeds manager Dennis Wise will join Newcastle's coaching staff after the two clubs agreed a compensation fee.
The 41-year-old will depart Elland Road tomorrow after preparing the side for their Coca-Cola League One clash at Southend.
A club statement read: "We have agreed a compensation package with Newcastle for the services of our manager Dennis Wise and he will part company with the club on Tuesday, after completing the preparations for our game at Southend that evening.
"Newcastle had approached us for permission to speak with Dennis on Friday and since then things have happened very quickly.
"We will always be grateful to Dennis for the way he has turned things around at the club on the playing side and he goes with our best wishes for the future.
"We are not prepared to comment on the inevitable speculation that will now follow about who will replace Dennis. That is not the way we do our business at this club."
Keegan took control of the Magpies this month and has since failed to convince Newcastle hero Alan Shearer to come on board as his number two.