Abstract Stabilization/solidification technology (S/S), in which contaminated marine sediments are mixed with cement and other binding agents have shown to be a promising remediation technique. The major advantage of S/S over other contaminated sediments remediation techniques is that dredged material can be transformed from a soft material into a filling material with favorable geotechnical properties. Reduced contaminant transport from the treated material is achieved simultaneously. This paper summarizes a study investigating how amendments (additions) may improve the mechanical properties and reduce leaching of heavy metals of two cement-stabilized marine harbor sediments from the cities of Bergen and Hammerfest, Norway. The deployed amendments comprised granulated blast furnace slag (Merit®), cement kiln dust, fly ash, gypsum, sand, iron sulfide, and microsilica. The use of amendments was observed to improve the strength of cement-stabilized soft and wet sediments, where the use of granulated blast furnace slag (Merit) resulted in the greatest inprovement. Cement stabilization resulted in a reduced leaching of lead, whereas the leaching of copper and chromium from Hammerfest sediments increased substantially. In order to achieve the lowest total net transport of contaminants through the material, S/S recipes for environmental projects should not only be optimized with regard to physical strength, but also with regard to leaching and permeability.