King scored his eighth goal of this campaign to send the Foxes on their way to another fine home win that sends them flying up to fourteenth in the Championship table, just five points outside of the play-off places.
Sven Goran-Eriksson made just one change to the team that fell to a 2-0 loss at the hands of Bristol City just over a week ago. Roman Bednar - on loan from the Premier League's West Brom - made his debut up front in place of the impressive Steve Howard.
Eriksson's other recent loan acquisition - Wigan 'keeper Chris Kirkland - was agonisingly ruled out of contention for a debut - suffering yet another injury.
A strong City side started the better of the two teams and held possession well, but the Forest back line looked strong and the likes of Vassell and Bednar were left frustrated by the fine form of Forest 'keeper Lee Camp as the Foxes frontline worked tirelessly only to see several efforts stopped well.
But, as the game progressed, Leicester looked ever more comfortable on the ball and dominated play in the middle of the park, producing some excellent free flowing football that nearly culminated in the games opening goal.
Darius Vassell picked up a ball from Richie Wellens but, just as it looked as if the former England striker had opened his account for the Foxes, Luke Chambers was able to prevent the ball crossing the line with a wonderful piece of defending.
An injury to Forest striker Dele Adebola forced Billy Davies into an early substitution towards the end of the first half, and his decision to introduce Robert Earnshaw to the Walkers Stadium crowd nearly proved a masterstroke.
An awfully misjudged defensive header from Kyle Naughton was too weak to reach Chris Weale and Earnshaw pounced on the ball. But, the Welsh striker was unable to find the net as Weale instictively rushed out to block the strike.
After the break, it was Leicester who continued to search for the lead - and they will feel they should have been awarded a penalty when Vassell was involved in an attacking move around the Forest 18 yard box.
The former England striker twisted and turned to find space for a shot, but was pulled back by defender Chris Gunter but referee Michael Oliver ignored the protests.
Vassell was clearly fired up and continued to show the Foxes faithful exactly why Eriksson brought him to the Walkers Stadium when he picked the ball up 25 yards from goal. With four defenders in his path the striker stormed into the box and his shot come cross was met by Andy King who slid the ball home to give the home side a much deserved lead.
Chances began to open up for both sides and moments later the referee was faced with another tough penalty decision - this time the away side were stunned to see the referee ignore the claims.
Robert Earnshaw was sent tumbling in the box by Greg Cunningham as he tried to reach an Aaron Ramsey through-ball but yet again Michael Oliver waved play on much to the frustration of the travelling Forest fans.
The Foxes grew in confidence with the late introductions of Lloyd Dyer and Steve Howard and it was the veteran striker who should have wrapped up all three points with just minutes left on the clock.
A Gallagher cross was met by Howard but his shot was stopped superbly from close range by 'keeper Lee Camp.
Despite wasting several chances to extend their lead, the Foxes held on comfortably to silence another East Midlands rival - just over two weeks after that incredible display against Derby County.
The win sees Leicester climb up to fourteenth in the Championship table.