Julian Alvarez and Nathan Ake opened the scoring for the champions, who have beaten Fulham in their last 15 league meetings, and top the table with 12 points from four matches.
But clinical Haaland stole the show yet again with another predatory performance at the Etihad Stadium.
“I’m back. No problem for me. I’m always hungry. It’s a new season and I’m ready for it,” Haaland said of his hattrick.
“It started a bit sloppy but we ended in a good way. Important win. We go into the international break having won four in four. Good start to the season.”
Fulham, who had scored an equaliser through Tim Ream before being overrun, have four points from their four matches.
Haaland, who broke several scoring records last term, added another by becoming the fastest player to reach 50 goal involvements in the Premier League with his first of the afternoon. He now has 43 goals and nine assists in 39 Premier League appearances.
The Norwegian has netted six goals this season and five Premier League hattricks since joining City last season.
Controversial moment
The most controversial moment of the match was Ake’s goal seconds before half-time, which appeared set to be ruled out as Manuel Akanji was standing in an offside position in front of Fulham goalkeeper Bernd Leno and jumped over the ball on its way into the net. But VAR ruled that the goal was valid.
Fulham manager Marco Silva vented his frustration over the decision to referee Michael Oliver.
Alvarez had broken open what had been a pedestrian affair in the 31st minute when Haaland fired a pass square across the edge of the six-yard box that the Argentine tapped in. However, Fulham were back on level terms two minutes later through Ream.
“Every year is like this at this club. We start a bit late and a bit sloppy because we play right until the last game (of every season) because we are the best club,” Haaland said. “It is how it is. We will only get better and better from here.”
Ake then put City 2-1 ahead before Alvarez repaid Haaland in the second half when his flicked pass found the striker behind Fulham’s defence just before the hour and the Norwegian scored.
Haaland then converted a 70th minute penalty after Alvarez was taken down by Issa Diop. The in-form striker sent Leno the wrong way, launching the ball into the top corner.
He was not done for the day, however, completing his hattrick deep into added time when he fired home a low first-time left-foot shot from a pass by Sergio Gomez.
With City boss Pep Guardiola still recovering from back surgery, assistant manager Juanma Lillo took charge.
“I think (Guardiola) misses us, we also miss him sometimes too,” Haaland said. “So we look forward to having him back.”