Cameroon, playing the Netherlands for the first time in a competitive match, adopted a cautious approach at Stade du Hainaut, with five players in the back line and four in front of them for the majority of the game.
The tactics worked until a sweeping Dutch move in which Shanice van de Sanden's inch-perfect cross found Arsenal forward Miedema, who powered home a thumping header in the 41st minute.
Cameroon responded almost immediately as winger Gabrielle Aboudi Onguene timed her run perfectly to latch on to a long ball before beating goalkeeper Sari van Veenendaal for an easy finish.
Netherlands, who beat New Zealand in their opening match, were back on the front foot in the second half after a cleverly worked free kick allowed centre back Dominique Bloodworth to score her first international goal from close range.
Cameroon substitute Henriette Akaba came close to an equaliser in the closing stages before Miedema scored her second goal to put the result beyond doubt.
It was Miedema's 60th goal for the Netherlands as she overtook former striker Manon Melis to become their all-time top scorer.
"It is something special, something I'm only going to live once and it's a special experience for me," the 22-year-old Miedema said.
"It's a World Cup -- you score a goal, so I think you can cheer and be a little crazy about it."
Netherlands top Group E after winning back-to-back World Cup matches for the first time, before Canada's evening kick-off against New Zealand in Grenoble.
"I'm glad we won. In a couple of stages we played better than the previous game but we struggled as well," Netherlands coach Sarina Wiegman said.
"We are now qualified for the next round. But who is better as an opponent? Is it Japan, Sweden or England? I think it's dangerous doing maths. Let's just play the Canada game first."
Netherlands will meet Canada in their final group-stage match in Reims on Thursday, while Cameroon face New Zealand on the same day at Montpellier.
(Reporting by Hardik Vyas in Bengaluru, editing by Pritha Sarkar and Clare Fallon)
