Production and handling of engineered nanomaterials (ENMs) can yield worker exposure to these materials with the potential for unforeseen negative health effects. Biomonitoring enables regular exposure and health assessment and an effective risk management. We aimed to identify factors influencing biomonitoring acceptance according to hierarchical positions of ENM producers. Managers and workers were invited to complete an online questionnaire. Forty-three companies producing or handling ENMs such as titanium dioxide (61%) and multi-walled carbon nanotubes (44%) participated. The majority of managers (72%) and all workers responded positively to participating in biomonitoring studies. The main reasons for refusing participation included concerns about data confidentiality and sufficient knowledge about ENM health and safety. Acquisitions of individual study results, improvement of workers' safety, and help to the development of ENM-specific health and safety practice were among the most valuable reasons for positively considering participation. All workers indicated feeling comfortable with biomonitoring procedures of exhaled air sampling-about half were similarly comfortable with exhaled breath condensate, urine, and buccal cell sampling. The majority of both workers and managers stated that participation in a biomonitoring program should take place during working hours. Although our survey only had limited participation, our results are useful in designing appropriate biomonitoring programs for workers exposed to ENMs.