The detection structure for a MEMS accelerometer is formed by a substrate; a first movable mass and a second movable mass which extend at a distance from each other, suspended on the substrate and which are configured to undergo a movement, with respect to the substrate, in response to an acceleration. The detection structure also has a first movable electrode integral with the first movable mass; a second movable electrode integral with the second movable mass; a first fixed electrode integral with the substrate and configured to form, with the first movable electrode, a first variable capacitor; and a second fixed electrode integral with the substrate and configured to form, with the second movable electrode, a second variable capacitor. The detection structure has an insulation region, of electrically insulating material, which is suspended on the substrate and extends between the first movable mass and the second movable mass.