Spread crushed strawberries on the bottom of a 9x13 inch baking pan. Evenly sprinkle strawberries with the dry gelatin powder, and top with mini marshmallows.
Prepare the cake mix as directed on the package, and pour on top of the marshmallows. Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 40 to 50 minutes. Cool in the pan for 15 minutes. Run a knife around the pan to loosen the sides, and turn the cake out onto a serving tray. Store cake in the refrigerator.