To date, the use and translation of nanomedicine from the laboratory to the clinic has been relatively slow. Among other issues, one of the reasons for this tardiness is the lack of the availability of quick and reliable toxicity tools for the screening of nanomaterials (NMs). In this investigation, we apply a flow cytometry-based method for the detection of nanomaterial-induced oxidative stress by measurement of reactive oxygen species production in specific leukocyte subpopulations in human whole blood. The screening of a panel of relevant nanomedical-associated materials (liposomes, silica, iron oxide and functionalized single-walled carbon nanotubes) demonstrated that only the carbon nanotubes induced oxidative stress in human circulating leukocytes. In summary, we apply and corroborate a flow cytometry-based method for the simple and effective measurement of NM-induced oxidative stress in human blood subpopulations after realistic and relevant exposure scenarios which is extremely useful in future toxicological applications.