The Norway international scored his 31st and 32nd top-flight goals of the campaign after a stunning John Stones opener, but Kelechi Iheanacho bagged a consolation at his former stomping ground as the Foxes gave the champions a few last-minute scares in their first game under Dean Smith.
Before Smith experienced his first taste of Haaland-inflicted suffering, City broke the deadlock after just five minutes with a goal that the Norwegian marksman would have been proud of scoring himself.
A Riyad Mahrez corner was sent clear by Wout Faes, but the ball continued to bounce off heads in and around the penalty area, and Stones proceeded to fire home a sumptuous half-volley from the edge of the box from Rodri's knock-down.
Leicester barely had time to regroup before Jack Grealish's cross struck the outstretched arm of Wilfred Ndidi, and a quick VAR check ended with referee Darren England pointing to the spot.
Haaland did not get the cleanest connection on his spot kick, but the 22-year-old picked out the bottom corner to double City's lead in the 13th minute; Daniel Iversen dived the right way, but there was little that the Leicester shot-stopper could do.
Things went from bad to worse for the travelling Leicester faithful in the 25th minute, as Kevin De Bruyne stole in to intercept Kiernan Dewsbury-Hall's misplaced pass, and as has been the case throughout the season, the Belgian picked out the run of Haaland for the Scandinavian sensation to chip over the charging Iversen.
Haaland's second of the day saw the history-making marksman equal the record for the most goals in a 38-game Premier League season, matching Mohamed Salah's tally of 32 from the 2017-18 season, but he would not get the chance to overtake the Egyptian as he was encased in bubble wrap by Guardiola at half time.
Leicester boss Smith also made a couple of mid-game alterations - switching out Victor Kristiansen and Jamie Vardy for Luke Thomas and Iheanacho - but keeping the scoreline respectable was the Foxes' main goal for the second 45.
Leicester had Iversen to thank for a stunning save from ex-Foxes attacker Mahrez in the 61st minute - 10 minutes before Leicester's first shot on target, which was a tame Dennis Praet attempt into the gloves of Ederson.
However, Smith's side were not giving up the ghost and pulled one back in the 75th minute through former Man City attacker Iheanacho, who poked home into an empty net after Harry Souttar's header was parried into his path by Ederson.
Man City's plethora of changes had evidently disrupted their momentum, and the final exchanges could have been a very uncomfortable affair for the hosts after Ruben Dias's error allowed James Maddison a clean run through on goal in the 85th minute, but Ederson stuck a leg out to prevent the Englishman finding the bottom corner.
Iheanacho also hit the post in added time following a glorious through ball from Maddison as Leicester ended the game on top, but there was no stopping the Man City juggernaut, as Pep Guardiola's side now prepare for the second leg of their Champions League quarter-final with Bayern Munich on Wednesday.
Meanwhile, Leicester stay 19th - two points adrift of safety with seven games to go - and their next game comes at home to Wolverhampton Wanderers on April 22.