Mercury pollution poses a severe threat to human health. To remove Hg(2+) from contaminated water, we synthesized Hg(2+)-trapping beads that include oligo-thymidine functionalities that can form thymine-Hg(II)-thymine base pairs on the solid support. The beads can selectively trap Hg(2+) even in the presence of other metal cations. More interestingly, Hg(2+)-trapping efficiency was higher in the presence of the co-existing cations. Thus, the developed Hg(2+)-trapping beads can capture Hg(2+) without affecting the mineral balance of water so much. The Hg(2+)-trapping beads presented here show promise for removing Hg(2+) from environmental water.