Weitz previously directed the drama About A Boy and the fantasy adventure The Golden Compass, a project he initially departed in 2005 because he felt the scope of the story was too large and didn't want to disappoint fans.
He eventually rejoined after the book's author Philip Pullman asked him to reconsider. The New Line film went on to gross $372.2m worldwide, although the $70.1m North American gross fell far short of expectations and the franchise was shelved.
Summit and Hardwicke parted on amicable terms after a disagreement on how to adapt Stephenie Meyer's second book. It is understood Hardwicke, who scored the biggest opening weekend in history for a female director when Twilight grossed $69.6m in its first three days in November, was also keen to have more time to develop the project.
Twilight crossed $150m in North America this weekend and has amassed more than $200m worldwide.
Screenwriter Melissa Rosenberg delivered a draft for New Moon the weekend Twilight launched in theatres. In the sequel the character of Bella, played by Kristen Stewart, finds herself drawn into the world of the werewolves following the departure of her vampire love Edward Cullen, played by Robert Pattinson. Summit intends to move into production in the next few months and plans a late 2009 or early 2010 release.
'Thinking long and hard about how to turn New Moon into the amazing movie we know it will be, and working with Stephenie Meyer to find the right candidate, we are thrilled to announce Chris Weitz as director of the film,' said Summit's production president Erik Feig, who will oversee New Moon for the studio along with director of production Gillian Bohrer.
'The extraordinary world that Stephenie has created has millions of fans, and it will be my duty to protect on their behalf the characters, themes and story they love,' Weitz said. 'This is not a task to be taken lightly, and I will put every effort into realising a beautiful film to stand alongside a beautiful book.'
Weitz is represented by WMA and by Alex Kohner of Morris, Yorn, Barnes & Levine.