Millwall have agreed a deal to sign Brighton goalkeeper John Sullivan, while Alan Dunne has penned a new contract with the Lions.
Kenny Jackett is keen to strengthen his squad as early in the summer as possible and will bring in Sullivan on 1st July.
The highly-rated 21-year-old made 13 appearances for the Seagulls and is looking forward to challenging for a regular place at The Den.
"It is a great chance to come to a big club like Millwall that should be in the Championship," he told the club's official website.
"Hopefully next year we can try and have another go at getting back to that level.
"I'm exited at the prospect of trying to get into our team next year.
"I know David Forde, I know he's a great keeper, and so there will be some good competition."
Jackett has also tied Dunne to a one-year deal and the right-back is happy to be remaining with the club after enjoying an excellent end to the season.
"I'm delighted to be staying and I'm looking forward to next season already," said Dunne, who had struggled with a foot problem early in the 2008/9 campaign.
"Losing the play-off final was a big disappointment for everyone, but we're over it now and we're setting our sights on automatic promotion."