It looked like Sven-Goran Eriksson would get the better of Steve McClaren and lead Leicester to their first win at the City Ground since 1972 when quickfire goals from David Nugent and Gelson Fernandes gave the Foxes the half-time advantage.
It seemed plain sailing for the visitors but, after Lewis McGugan had pulled a goal back from the penalty spot, Kasper Schmeichel was sent off for taking his protests too far and Eriksson's 10 men could not hang on as Boateng levelled things up deep into stoppage time.
McClaren's side were masters of their own downfall with individual mistakes leading to both Leicester goals.
Lee Camp produced a point-blank save to keep out a powerful Nugent header and saved from Sol Bamba early on, but there was little the Forest goalkeeper could do to prevent the opening goal.
Jonathan Greening squandered possession to Fernandes in midfield and the Swiss raced towards the penalty area before unselfishly setting up Nugent to score from close range after 18 minutes.
Three minutes later it was 2-0. Big centre-half Wes Morgan tried to find Boateng but his pass was intercepted by Neil Danns.
Danns went round Camp but saw his shot cleared off the line by Chris Gunter. However, the ball fell invitingly into the path of Fernandes who could not miss from six yards out.
Forest should have pulled a goal back just after the half-hour mark. Gunter whipped in a delightful cross but Matt Derbyshire did not connect properly with his header.
Derbyshire was replaced by Ishmael Miller at half-time, with Robbie Findley also coming on up front for David McGoldrick as McClaren attempted to liven up his team.
The two substitutes combined midway through the second half when Miller flicked the ball on to Findley who shot straight at Schmeichel.
Schmeichel had to be alert again soon afterwards, this time to deny Miller.
Forest got themselves back into the game in the 79th minute when Matt Mills was adjudged to have handled the ball. Schmeichel was booked for contesting the decision of referee Jonathan Moss and McGugan dispatched the spot-kick.
Schmeichel then received a second yellow card for kicking away the ball, resulting in Danns being sacrificed so that back-up keeper Chris Weale could go in goal.
McClaren's team threw everything at Leicester in search of an equaliser and it came in the fourth minute of stoppage time when Boateng tapped home Chris Cohen's cross from three yards out.