Manchester City took a hat-trick in the second half after beating Crystal Palace 4-2 at the Etihad Stadium on Saturday.
Haaland, who averaged around one goal per game in the Bundesliga for Borussia Dortmund before moving to City in June, has now scored six times in his opening four league appearances for Pep Guardiola’s side.
The win moves City to top the table with Brighton & Hove Albion on 10 points. Castle are in thirteenth spot with four focuses from their initial four matches.
Haaland were given a standing ovation six minutes from the end, but at halftime City were looking at a possible repeat of their 2-0 home loss to Palace last season.
A goal from John Stones in the fourth minute put Patrick Vieira’s team ahead and the visitors doubled their lead when an unmarked Joachim Anderson in the 21st minute entered a header from an Abrecchi Eze corner.
City struggled to find their flow, but began an almost inevitable comeback in the 53rd when Bernardo Silva cut to the right and his low shot deflected slightly and hit goalkeeper Vicente Guetta.
Guardiola then, at that point, made a twofold replacement and Phil Foden was moved to one side and in no less than brief he conveyed a pinpoint cross, which Haaland met with a fine coating header.
Following a clever move from Silva, the striker turned the ball around and saved the best to show a pass to Ilke Gundogan for the last time and then caught Joel Ward firing into the bottom corner.
It’s about trying to continue what we’re doing. It was about small adjustments and we did that and got the result. It’s a mindset that we trust each other and we know opportunities will come. It is about keeping going.
It is a reminder that we have to become better, train harder and grow. When we play at home, we should not score opening goals. He said it is about working hard.