This paper describes the lasting effect of sand capping techniques on nutrient release reduction from contaminated sediments. Bottom sediments in Tokyo Bay are very contaminated as the results of eutrophication behavior. From the sediments, a large amount of nutrients are released into seawater bodies. In order to know the effect of the sand capping technique on nutrient release reduction and its lasting effect, we carried out the undisturbed sediment sampling at Yokohama Port. Then we carried out the laboratory tests to estimate the nutrient release rate. From the study, it is concluded that the sand capping technique has a still effect on nutrient release reduction from the contaminated sediments, and the effectiveness is dependent upon the thickness of mud layer accumulated on the capped sand.