Miedema's goals came either side of a close-range Dominique Bloodworth strike for the European champions in Valenciennes, with Gabrielle Aboudi Onguene netting for Cameroon.
The Netherlands have won two out of two in Group E and their place in the knockout rounds is therefore secure before they take on Canada in Reims next week.
Sarina Wiegman's team were helped by a huge Dutch support which turned the Stade du Hainaut into a sea of orange, with around 15,000 fans expected in the northern French town which lies only a two-hour drive across Belgium from the southern Netherlands.
Those supporters saw their team take the lead in the 41st minute through a fine goal, with exciting winger Shanice van de Sanden playing a one-two with Jackie Groenen before crossing for Miedema to head home.
The lead lasted only two minutes, though, with Aboudi Onguene latching onto a long ball forward and rounding goalkeeper Sari van Veenendaal to score.
However, the Dutch restored their lead within three minutes of the second half starting, with the Indomitable Lionesses failing to deal with a well-worked free-kick and the ball falling for defender Bloodworth -- who plays with Miedema at Arsenal -- to convert.
Substitute Lineth Beerensteyn then played in Miedema to run through and blast in their third late on, with that strike also taking the 22-year-old forward onto 60 international goals and making her the all-time top scorer for the Netherlands women's side.
Canada can also clinch qualification for the last 16 with a win over New Zealand later in Grenoble.