The show's first run, which starred Jessica Raine and Miranda Hart, came to a close last night with 9.2m viewers.
The ratings brought the show's average audience to 8.7m, making it the biggest new series on the channel since records began in 2001.
The BBC's controller of drama commissioning Ben Stephenson described the show as "a phenomenon that has won the hearts of the nation", while BBC One's controller Danny Cohen claimed that writer Heidi Thomas and production company Neal Street have "brought a new kind of grit and risk to period drama".
Meanwhile, Thomas said: "When [Call the Midwife author] Jennifer Worth was dying, I took her hands in mine and promised I'd do everything in my power to make her books sing as a drama.
"She will be looking down now from the heaven she undoubtedly believed in, and smiling. That means more to me than I can say."
Call the Midwife has already been renewed for a second series by BBC One.