Municipal Solid Waste Incineration Bottom Ash (MSWI BA) is of increasing interest as a secondary construction material worldwide. In most cases, MSWI BA is used in isolated conditions. However, according to the Dutch Green Deal B-076 in 2012, by 2020 all MSWI BA should be used in a non-sealed environment in the Netherlands. However, freshly produced. MSWI BA normally does not match environmental legislation due to high leaching of chlorides, sulfates, and potentially toxic elements. Because different particle size fractions of MSWI BA are of interest for designing optimized concrete recipes, it is beneficial to analyze the whole range of MSWI BA fractions in detail. In this study, 14 size fractions of MSWI BA were analyzed to determine the total elemental composition and leaching capacity, mineralogical composition, and shape variety of fine particles. From the point of view of mineralogical composition, 6 particle size fractions (<180 μm, 180–500 μm, 0.5–1 mm, 1–4 mm, 4–22 mm, > 22 mm) can be distinguished. All together the analyses showed that almost all fractions of the investigated MSWI BA can be used as secondary building materials. However, because the leaching of fine fractions is 5–10 times higher than of coarse fractions, all these fractions must undergo various treatments to allow them to match the environmental legislation. Thus, to decontaminate MSWI BA from potentially toxic elements, a division into three size groups is suggested: fine (<125 μm), medium (125 μm - 1 mm), and coarse fractions (over 1 mm).