Anja Mittag put two-time champion Germany ahead in the sixth minute with her 37th international goal, chipping past Ingrid Hjelmseth after the goalkeeper failed to control Dzsenifer Marozsan's shot.
Mjelde curled in a free kick from just outside the penalty area in the 61st minute for her 11th international goal.
Germany outshot Norway 27-4.
Both teams are 1-0-1 with four points, and Germany leads Group B on goal difference.
Germany closes group play against Thailand on Monday, when Norway faces Ivory Coast.
Later in the day, Wang Lisi scored in the first minute of stoppage time to give China a 1-0 victory over the Netherlands in Edmonton.
Wang took a pass in the penalty area and tapped the ball just inside the far post past Dutch goalkeeper Sari van Veenenedaal.
The last-ditch win puts China opening-group play record at 1-1-0 for three points.
The Netherlands, which beat New Zealand in its first-ever FIFA Women's World Cup match last Saturday, fell to 1-1-0 for three points.
Canada settled for a 0-0 draw against New Zealand in the night match at Commonwealth Stadium. The Canadians are 1-0-1 and sit atop Group A with four points.
New Zealand is now 0-1-1, placing it behind Canada, China and the Netherlands.
Also, Thanatta Chawong scored an insurance goal in the 75th minute which proved the difference and Thailand beat Ivory Coast 3-2 in Ottawa.
Thailand improved its group record to 1-1-0 with three points while Ivory Coast, 10-0 losers to Germany in its opener, fell to 0-2-0.