The 66-year-old is in his third spell as Daggers boss, having returned to the club on 31 December 2015.
He failed to guide them to Football League safety last season, with the club now second in the National League after 36 matches.
"I feel the club is growing. I feel that it is right that I stay," he said.
"Dagenham & Redbridge is my club and when I do go, whether we are in this league or in League Two I would like to look back when I go that I have left all of the foundations for this club to grow again."
Still has been promoted three times from the top tier of non-league football; with Maidstone United in 1989, Dagenham in 2007 and Luton in 2014.
Dagenham marked his new deal with a 2-1 win over fellow promotion hopefuls Forest Green Rovers on Saturday, a victory that moves them one point above the Gloucestershire club.
However, both Forest Green and Tranmere in fourth have a game in hand, while leaders Lincoln have two matches in hand over Dagenham.
Dagenham & Redbridge manager John Still has signed a two-year contract extension, keeping him at the National League club until the summer of 2019.