The 34-year-old centre-half, who joined the Lions from Sheffield Wednesday in January, has committed himself to The Den until next summer.
Kenny Jackett's side are still in with a shout of a play-off place, currently lying three points off sixth spot with seven games to play.
And Purse, who supported the Lions as a boy, told the club's official website: "Whatever happens in the last seven games, I can only see things getting better and better for Millwall with the manager, the set-up and the squad we have here.
"I'm really looking forward to being part of it."
Source: PA
Source: PA