Styles is known to be a ladies' man. He recently broke up with singer Taylor Swift after having a hyped relationship with her, and he has been linked to various women time and again.
However, his father is worried that he will build a bad guy's image for himself unlike his true self.
"Des is worried that Harry is emerging as a lad who treats girls badly, dumps them and moves on without much remorse. He told Harry he's part of a clean-cut teenage band and although girls love them, he needs to treat them right," dailystar.co.uk quoted a source as saying.
"He doesn't want his son to develop haters, with girls likening him to love cheat Ashley Cole. He told Harry to ride the wave and live the dream, but he's concerned his son is getting a bad reputation, which is unjustified as he's a kind-hearted soul," the source added.
Styles' father has also warned him about his future involvement with women.
"He's also advised Harry not to get involved with anyone again the way he did with Taylor Swift, saying he should focus solely on the tour. Harry listens to his dad. He looks up to him and they're very close," the source said.