The Northern Ireland international striker went on loan to Preston last week, in order to be able to play against Sheffield United on Saturday, and has now had a medical to finalise the switch.
He scored at Bramall Lane on his debut, and has signed a contract to keep him with the First Division club until the summer of 2005 after passing the medical, with the fee rising a further £300,000 depending upon appearances.
"I am pleased to just finally get it all sorted an I am happy to be here," Healy told the official Preston website. "I was interested straight away as soon as I knew.
"I sort of knew that Preston were interested, but the gaffer at Manchester United keeps things to himself. He told me that David Moyes was a good manager and that the club was going places, that there was a lot of young talent and was he happy to let me go here.
"It's not difficult to leave Manchester United, because I knew I wasn't going to get first team football and, at the end of the day, that's what I want to do and hopefully at Preston that will happen.
"We have got a good squad and a lot of young players. If it doesn't happen straight away I will just be patient. Hopefully I will settle in as quickly as possible. I think the goal at Sheffield United helped.
"Preston is going places; the ground is being built, there are some great young players coming through and the squad is still relatively young, with players to reach their prime.
"If we keep the squad together the who knows, hopefully we can be in the Premiership in the next couple of years."
