Graphene and its derivatives are an emerging class of carbon nanomaterial with great potential for a broad range of industrial and consumer applications. However, their increasing production and use is expected to result in release of nano-sized graphene platelets into the environment, where they may interact with chemical pollutants modifying their fate and toxic potential. The objective of this study was to assess whether graphene nanoplatelets can act as vector for aromatic environmental pollutants increasing their cellular uptake and associated hazardous effects in vitro. For this purpose, cell cultures of the topminnow fish (Poeciliopsis lucida) hepatoma cell line PLHC-1 were simultaneously (and successively) exposed to graphene nanoplatelets (graphene oxide (GO) or carboxyl graphene (CXYG)) and an aryl hydrocarbon receptor (AhR) agonist (β-naphthoflavone (β-NF), benzo(k)fluoranthene (BkF) or 3,3′,4,4′,5,5′-hexachlorobiphenyl (PCB169)). Following exposure cytochrome P450 1A (Cyp1A) induction was assessed by measuring cyp1A mRNA expression levels using reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) and Cyp1A-dependent ethoxyresorufin-O-deethylase (EROD) activity. It was observed that pre- and co-exposure of cells to GO and CXYG nanoplatelets had a potentiating effect on β-NF, BkF, and PCB169-dependent Cyp1A induction suggesting that graphene nanoplatelets increase the effective concentration of AhR agonists by facilitating their passive diffusion into the cells by damaging the cells' plasma membrane and/or by transporting them over the plasma membrane via a Trojan horse-like mechanism. The results demonstrate the existence of combination effects between nanomaterials and environmental pollutants and stress the importance of considering these effects when evaluating their respective hazard. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 1192–1204, 2015.