Single-walled carbon nanotubes (SWNT) have extremely high affinity for hydrophobic organic contaminants, considerably higher than natural or refractory (e.g., soot and detrital) carbon found in sediments. To evaluate the effect of sediment-associated SWNT on contaminant uptake from sediments by infaunal deposit feeders, we have conducted a comparative bioaccumulation study using two infaunal estuarine invertebrates. The deposit-feeding meiobenthic copepod Amphiascus tenuiremis and the deposit/suspension-feeding polychaete Streblospio benedicti were exposed to hydrophobic organic contaminants (HOCs) including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, and polybrominated diphenyl ethers for 14 days in the presence of sediment amended with (1) SWNTs, (2) NIST diesel soot, or (3) no carbon amendment. Coaddition of SWNT to sediments significantly reduced bioaccumulation of HOCs in S. benedicti; however, soot addition tended to increase the bioaccumulation of these same compounds in the polychaete worm. Bioaccumulation of HOCs from sediments by copepods (A. tenuiremis) was less dependent on black carbon addition to sediment; neither SWNT nor soot significantly impacted bioaccumulation of PAHs from sediment by this organism. Exposure of both copepods and polychaetes to radiolabeled (14C) SWNT in estuarine sediments revealed that these organisms did not assimilate these materials into their tissues, although S. benedicti did ingest 14C-SWNT, as fecal rods from this organism contained identical 14C activity as that of the sediment to which the worms were exposed.