His soon to be new charges beat Liverpool in a penalty shootout at Wembley to win the English League Cup, the first silverware on offer in the current campaign.
The match had finished tied at 1-1 after extra time.
City's second choice goalkeeper Willy Caballero repaid the faith placed in him by current manager Manuel Pellegrini with a stunning hat-trick of saves in the penalty finale.
It left the way for Yaya Toure to clinch it 3-1 with the decisive penalty, sparking scenes of celebration among the City players and supporters.
A goal early in the second half from Fernandinho after a dreadful blunder by Liverpool goalkeeper Simon Mignolet put City ahead before Philippe Coutinho leveled in the 83rd minute with a crisp low shot, his side's first shot on target of the final.
Before that, Raheem Sterling wasted two chances to put the game out of Liverpool's reach and Sergio Aguero was upended by Alberto Moreno with strong penalty claims waved away.
Mignolet, who had performed heroics in the fist half when turning away an Aguero shot onto the post, atoned for failing to keep out Fernandinho's shot-cum-cross from an angle with crucial saves to deny Toure in the closing moments and Aguero in the first half of extra time.
Argentina's Caballero, who has endured a difficult time since following Pellegrini from Malaga, also showed his worth by saving from Divock Origi's header.
It left the two sides to battle it out from the penalty spot, with Liverpool taking an early lead as Fernandinho's effort hit the post.
But it swiftly turned around as Caballero kept out efforts from Lucas, Coutinho and Adam Lallana, ending the match in tears as he was mobbed by teammates.
"It's a huge moment for me and my family," he told Sky Sports.
It was Manchester City's second League Cup triumph in three years and could act as a springboard as it did in the season before last for a successful challenge for the English Premier League title.
With a game in hand it trails leader Leicester by nine points and is also heading for the quarterfinals of the Champions League after an excellent 3-1 last 16, first leg win at Dynamo Kiev in midweek
For Liverpool, it was a bitter disappointment in Jurgen Klopp's first season in charge, with only the Europa League, where it plays Manchester United in the last 16, offering any hope of silverware.
The two sides will also meet again in midweek in an English Premier League match, with City hoping to cut the gap at the top. Its regular goalkeeper Joe Hart, who has sat out the League Cup campaign, will likely return with Caballero dropping to his normal place on the bench after his heroics.
Barca marches on
Meanwhile in Spain's La Liga, Guardiola's old club Barcelona kept its vice-like grip on the title race with a 2-1 win over Sevilla later Sunday.
Vitolo gave the impressive visitor an early lead in the Nou Camp before Lionel Messi leveled with a brilliant free kick before halftime.
Barca's winner from Gerard Pique came just after the break, set up by Luis Suarez.
It leaves them eight points clear of second placed Atletico Madrid, with arch rival Real Madrid a further four points adrift, extending an unbeaten run to 34 games.