The Wales coach insisted his squad were "no monks" and Wales have had some drink-related disciplinary issues in recent years.
But Gatland praised his squad's commitment to becoming world champions - comments which sit in stark contrast to the situation in the England camp.
On Thursday, the Rugby Football Union announced they had launched an investigation into all allegations of player misconduct during England's ill-fated World Cup campaign.
"We have had our problems in the past but these guys have been great ambassadors in this campaign for Wales," Gatland said.
"We have seen a sea shift in terms of professionalism. The guys knew we were in pretty good shape heading into the World Cup and if we looked after ourselves on and off the field we can make an impact and I think we have done that.
"There has been a lot made of us that we are like monks and there has been an alcohol ban. It is completely untrue.
"There has been no alcohol ban in this squad. A lot of the stuff has been self-imposed by the players.
"A couple of nights the boys have gone back to the hotel and we have had a drink in the hotel.
"A couple of times we have spoken with Sam (Warburton) and the senior players about putting the curfew on when the players come back after going out. You can't keep a lid on everything.
"As a fellow coach, and there are a lot of good friends of mine in that English set-up, I don't take any pleasure and the Welsh team don't take any pleasure in the criticism being heaped on England.
"But I just want to say we are no monks, we are not whiter than white."
Gatland is confident Wales will not miss a beat in Saturday's semi-final against France, despite being forced to replace Rhys Priestland with James Hook at fly-half.
Priestland has failed to recover from a shoulder injury in time - but Wales have an embarrassment of riches at fly-half.
Hook will start the game with Test centurion Stephen Jones named on the bench in an otherwise unchanged team from Wales' quarter-final victory over Ireland.
"We have been very impressed by the way Rhys has played. He's got better from game to game but we've got a lot of experience to come into that position," said Gatland.
"We put James Hook into the side. He's excited about his opportunity. We know how capable he is.
"He's been running there and looked really sharp in the last two weeks of training.
"Someone like the class of James Hook coming into the side and Stephen Jones on the bench shows what a good position we're in."
Unlike Priestland, Luke Charteris succeeded in overcoming the shoulder injury which forced him off at half-time against Ireland.
Charteris had made a monumental 16 tackles by the interval and feared he may have to join Priestland on the sidelines for the biggest game of his career.
Despite the size of the occasion, Charteris insisted he would have declared himself unavailable rather than risk letting Wales down on their biggest stage since 1987.
"There was that fear the first few days but the coaching staff gave me the time to prove my fitness. I'm grateful for that," Charteris said.
"I had a really good knock to it. I have missed some training but the physios have done a good job. There's been a lot of work from them.
"I wouldn't risk the team's goals for my personal one. If I felt that I wasn't right and couldn't contribute fully, I would pull out."
Charteris and Toby Faletau are level on top of the World Cup tackling charts with 59 - and he is ready for another monumental encounter with the French back row.
"There's no holding back, it's a World Cup semi-final and we want to get to the final. I'll just last as long as I can," he said.
Wales have lost to France in six of their seven meetings, with their only victory coming as part of the Grand Slam campaign in 2008.
With Saturday's match being such a unique occasion, Wales captain Sam Warburton is putting no stock in the past.
"I've been involved in a squad to play France twice now and both times we lost but this is a World Cup and results have shown so far that anything can happen," said Warburton.
"I think it'll be a good game to watch. I don't think history counts for anything when it gets to the semi-final stage of a World Cup."
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