AIDEN O'Brien and Sid Nelson have followed John Marquis in signing new contracts with the club.
O'Brien, 21, has penned a two-year deal with the option of a 12-month extension while 19-year-old Nelson has signed a three-year deal.
Both players are academy products and made significant contributions following the appointment of Neil Harris as manager last season.
O'Brien started all 10 of Harris's games in charge, scoring his first two goals for the club.
Nelson started nine of those games and was part of a defence that kept three clean sheets as the Lions fought unsuccessfully to retain their Championship status.
Chief executive Andy Ambler told the club's official website: "Neil believes that the club's current crop of youngsters can play a big part in both the short and long-term future for Millwall, so retaining the services of these two talented players is an important step."