Cresswell has made a big impression at Leeds in progressing through the club's Academy and into the first team for whom the 19-year-old has had seven outings so far.
The York-born youngster has joined the London outfit until the end of the season and the defender has vowed to give his all for the Lions.
“I’m here on loan so I'm delighted to be here,” Cresswell told Millwall’s official website.
“I’m going to be giving my all for this club and for this moment in time I’m a Millwall player and I’ll do everything I can to help this club and I’m sure I’ll show you that.
“I think I’m a player who brings a lot of determination and a lot of aggression.
"I always give 100 per cent and I’ll try my very best."
Asked how the move had come about, Cresswell explained: "I came off international camp and I sat with my dad and we got chatting.
"We heard that Millwall were interested and we liked what they had to offer and we just pursued it.
"I think Millwall is a good club and it's a good club to learn at.
"I think it comes with a lot of pressure and expectation and I think that’s what I need and I’m looking forward to getting going."