The invention relates to a foam sealing strip (2, 2′, 2″) which is suitable for sealing, for example, a window frame (5) and which is impregnated for delayed elastic recovery, wherein the foam sealing strip (2, 2′, 2″) has, with reference to a cross section, two opposite narrow sides (3, 4) which, in the fitted state, each face the inner side or the outer side of the window frame (5), and wide sides suitable for bearing against the side of the window or soffit (6), wherein, furthermore, in the fully recovered state, at least one edge region of the cross section, which edge region is designed as a vertical region (15), is at a greater height from a base surface (F) provided on the wide side than an adjoining low-lying region in the width direction, wherein the vertical region and the low-lying region run in alignment with a longitudinal direction of the foam sealing strip (2, 2′, 2″) and, in the fully recovered state, a surface profile which is curved in cross section is provided on the surface opposite the base surface (F). For an advantageous configuration, the base surface (F) can be a flat surface and/or a tiered increase thereof can be provided by an impregnated foam sealing strip (2) and/or two edge regions designed as vertical regions can be provided.