Rooney, 22, said: "I think my boxing training was beneficial in my development as a footballer, especially breaking through to the Premier League at such a young age.
"I needed that extra bit of strength that the boxing training had given me.
"It made it easier to play than it might have been and it's helped me with the way my game is now."
Rooney has been a boxing fan since he started primary school, always watching the big fights on TV.
He trained with the dream that he might one day make it as a professional if he did not break through in football.
Rooney added: "All through my life - from the ages of six, seven and eight - when big fights were on television, I used to stay up with my dad to watch them.
"I've always loved watching boxing and I went boxing training for about three or four years when I was younger. It's a sport I've always been involved in. I was doing both boxing and football training at one stage when I was about 15.
"But Everton, who I was with at the time, said I had to concentrate on one of them and I opted for football."